From: Eduard Zingerman eddyz87@gmail.com
[ Upstream commit 6715df8d5d24655b9fd368e904028112b54c7de1 ]
This commits updates the following functions to allow reads from uninitialized stack locations when env->allow_uninit_stack option is enabled: - check_stack_read_fixed_off() - check_stack_range_initialized(), called from: - check_stack_read_var_off() - check_helper_mem_access()
Such change allows to relax logic in stacksafe() to treat STACK_MISC and STACK_INVALID in a same way and make the following stack slot configurations equivalent:
| Cached state | Current state | | stack slot | stack slot | |------------------+------------------| | STACK_INVALID or | STACK_INVALID or | | STACK_MISC | STACK_SPILL or | | | STACK_MISC or | | | STACK_ZERO or | | | STACK_DYNPTR |
This leads to significant verification speed gains (see below).
The idea was suggested by Andrii Nakryiko [1] and initial patch was created by Alexei Starovoitov [2].
Currently the env->allow_uninit_stack is allowed for programs loaded by users with CAP_PERFMON or CAP_SYS_ADMIN capabilities.
A number of test cases from verifier/*.c were expecting uninitialized stack access to be an error. These test cases were updated to execute in unprivileged mode (thus preserving the tests).
The test progs/test_global_func10.c expected "invalid indirect read from stack" error message because of the access to uninitialized memory region. This error is no longer possible in privileged mode. The test is updated to provoke an error "invalid indirect access to stack" because of access to invalid stack address (such error is not verified by progs/test_global_func*.c series of tests).
The following tests had to be removed because these can't be made unprivileged: - verifier/sock.c: - "sk_storage_get(map, skb->sk, &stack_value, 1): partially init stack_value" BPF_PROG_TYPE_SCHED_CLS programs are not executed in unprivileged mode. - verifier/var_off.c: - "indirect variable-offset stack access, max_off+size > max_initialized" - "indirect variable-offset stack access, uninitialized" These tests verify that access to uninitialized stack values is detected when stack offset is not a constant. However, variable stack access is prohibited in unprivileged mode, thus these tests are no longer valid.
* * *
Here is veristat log comparing this patch with current master on a set of selftest binaries listed in tools/testing/selftests/bpf/veristat.cfg and cilium BPF binaries (see [3]):
$ ./veristat -e file,prog,states -C -f 'states_pct<-30' master.log current.log File Program States (A) States (B) States (DIFF) -------------------------- -------------------------- ---------- ---------- ---------------- bpf_host.o tail_handle_ipv6_from_host 349 244 -105 (-30.09%) bpf_host.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_lxc.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_sock.o cil_sock4_connect 70 48 -22 (-31.43%) bpf_sock.o cil_sock4_sendmsg 68 46 -22 (-32.35%) bpf_xdp.o tail_handle_nat_fwd_ipv4 1554 803 -751 (-48.33%) bpf_xdp.o tail_lb_ipv4 6457 2473 -3984 (-61.70%) bpf_xdp.o tail_lb_ipv6 7249 3908 -3341 (-46.09%) pyperf600_bpf_loop.bpf.o on_event 287 145 -142 (-49.48%) strobemeta.bpf.o on_event 15915 4772 -11143 (-70.02%) strobemeta_nounroll2.bpf.o on_event 17087 3820 -13267 (-77.64%) xdp_synproxy_kern.bpf.o syncookie_tc 21271 6635 -14636 (-68.81%) xdp_synproxy_kern.bpf.o syncookie_xdp 23122 6024 -17098 (-73.95%) -------------------------- -------------------------- ---------- ---------- ----------------
Note: I limited selection by states_pct<-30%.
Inspection of differences in pyperf600_bpf_loop behavior shows that the following patch for the test removes almost all differences:
- a/tools/testing/selftests/bpf/progs/pyperf.h + b/tools/testing/selftests/bpf/progs/pyperf.h @ -266,8 +266,8 @ int __on_event(struct bpf_raw_tracepoint_args *ctx) }
if (event->pthread_match || !pidData->use_tls) { - void* frame_ptr; - FrameData frame; + void* frame_ptr = 0; + FrameData frame = {}; Symbol sym = {}; int cur_cpu = bpf_get_smp_processor_id();
W/o this patch the difference comes from the following pattern (for different variables):
static bool get_frame_data(... FrameData *frame ...) { ... bpf_probe_read_user(&frame->f_code, ...); if (!frame->f_code) return false; ... bpf_probe_read_user(&frame->co_name, ...); if (frame->co_name) ...; }
int __on_event(struct bpf_raw_tracepoint_args *ctx) { FrameData frame; ... get_frame_data(... &frame ...) // indirectly via a bpf_loop & callback ... }
SEC("raw_tracepoint/kfree_skb") int on_event(struct bpf_raw_tracepoint_args* ctx) { ... ret |= __on_event(ctx); ret |= __on_event(ctx); ... }
With regards to value `frame->co_name` the following is important: - Because of the conditional `if (!frame->f_code)` each call to __on_event() produces two states, one with `frame->co_name` marked as STACK_MISC, another with it as is (and marked STACK_INVALID on a first call). - The call to bpf_probe_read_user() does not mark stack slots corresponding to `&frame->co_name` as REG_LIVE_WRITTEN but it marks these slots as BPF_MISC, this happens because of the following loop in the check_helper_call():
for (i = 0; i < meta.access_size; i++) { err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1, false); if (err) return err; }
Note the size of the write, it is a one byte write for each byte touched by a helper. The BPF_B write does not lead to write marks for the target stack slot. - Which means that w/o this patch when second __on_event() call is verified `if (frame->co_name)` will propagate read marks first to a stack slot with STACK_MISC marks and second to a stack slot with STACK_INVALID marks and these states would be considered different.
[1] https://lore.kernel.org/bpf/CAEf4BzY3e+ZuC6HUa8dCiUovQRg2SzEk7M-dSkqNZyn=xEm... [2] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu... [3] git@github.com:anakryiko/cilium.git
Suggested-by: Andrii Nakryiko andrii@kernel.org Co-developed-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Eduard Zingerman eddyz87@gmail.com Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20230219200427.606541-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Maxim Mikityanskiy maxim@isovalent.com --- Backporting to address the complexity regression introduced by commit 71f656a50176 ("bpf: Fix to preserve reg parent/live fields when copying range info"), that affects Cilium built with LLVM 18.
kernel/bpf/verifier.c | 11 +- .../selftests/bpf/progs/test_global_func10.c | 31 +++ tools/testing/selftests/bpf/verifier/calls.c | 13 +- .../bpf/verifier/helper_access_var_len.c | 104 ++++++--- .../testing/selftests/bpf/verifier/int_ptr.c | 9 +- .../selftests/bpf/verifier/search_pruning.c | 13 +- tools/testing/selftests/bpf/verifier/sock.c | 27 --- .../selftests/bpf/verifier/spill_fill.c | 211 ++++++++++++++++++ .../testing/selftests/bpf/verifier/var_off.c | 52 ----- 9 files changed, 342 insertions(+), 129 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/test_global_func10.c
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index ad115ccc2fe0..60db311480d0 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2807,6 +2807,8 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, continue; if (type == STACK_MISC) continue; + if (type == STACK_INVALID && env->allow_uninit_stack) + continue; verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -2844,6 +2846,8 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, continue; if (type == STACK_ZERO) continue; + if (type == STACK_INVALID && env->allow_uninit_stack) + continue; verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -4300,7 +4304,8 @@ static int check_stack_range_initialized( stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; if (*stype == STACK_MISC) goto mark; - if (*stype == STACK_ZERO) { + if ((*stype == STACK_ZERO) || + (*stype == STACK_INVALID && env->allow_uninit_stack)) { if (clobber) { /* helper can write anything into the stack */ *stype = STACK_MISC; @@ -9492,6 +9497,10 @@ static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old, if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID) continue;
+ if (env->allow_uninit_stack && + old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_MISC) + continue; + /* explored stack has more populated slots than current stack * and these slots were used */ diff --git a/tools/testing/selftests/bpf/progs/test_global_func10.c b/tools/testing/selftests/bpf/progs/test_global_func10.c new file mode 100644 index 000000000000..8fba3f3649e2 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_global_func10.c @@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <stddef.h> +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +struct Small { + long x; +}; + +struct Big { + long x; + long y; +}; + +__noinline int foo(const struct Big *big) +{ + if (!big) + return 0; + + return bpf_get_prandom_u32() < big->y; +} + +SEC("cgroup_skb/ingress") +__failure __msg("invalid indirect access to stack") +int global_func10(struct __sk_buff *skb) +{ + const struct Small small = {.x = skb->len }; + + return foo((struct Big *)&small) ? 1 : 0; +} diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c index eb888c8479c3..4b0628cd2d03 100644 --- a/tools/testing/selftests/bpf/verifier/calls.c +++ b/tools/testing/selftests/bpf/verifier/calls.c @@ -1948,19 +1948,22 @@ * that fp-8 stack slot was unused in the fall-through * branch and will accept the program incorrectly */ - BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 2, 2), + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_JMP_IMM(BPF_JGT, BPF_REG_0, 2, 2), BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_JMP_IMM(BPF_JA, 0, 0, 0), BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), BPF_LD_MAP_FD(BPF_REG_1, 0), BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .fixup_map_hash_48b = { 6 }, - .errstr = "invalid indirect read from stack R2 off -8+0 size 8", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_XDP, + .fixup_map_hash_48b = { 7 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -8+0 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "calls: ctx read at start of subprog", diff --git a/tools/testing/selftests/bpf/verifier/helper_access_var_len.c b/tools/testing/selftests/bpf/verifier/helper_access_var_len.c index 0ab7f1dfc97a..0e24aa11c457 100644 --- a/tools/testing/selftests/bpf/verifier/helper_access_var_len.c +++ b/tools/testing/selftests/bpf/verifier/helper_access_var_len.c @@ -29,19 +29,30 @@ { "helper access to variable memory: stack, bitwise AND, zero included", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, -128), - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 64), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + /* use bitwise AND to limit r3 range to [0, 64] */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 64), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory at &fp[-64] is + * not initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+0 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 4 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+0 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: stack, bitwise AND + JMP, wrong max", @@ -183,20 +194,31 @@ { "helper access to variable memory: stack, JMP, no min check", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, -128), - BPF_JMP_IMM(BPF_JGT, BPF_REG_2, 64, 3), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + /* use JMP to limit r3 range to [0, 64] */ + BPF_JMP_IMM(BPF_JGT, BPF_REG_3, 64, 6), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory at &fp[-64] is + * not initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+0 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 4 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+0 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: stack, JMP (signed), no min check", @@ -564,29 +586,41 @@ { "helper access to variable memory: 8 bytes leak", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -64), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -56), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -48), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -40), + /* Note: fp[-32] left uninitialized */ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -24), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -16), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8), - BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, -128), - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 63), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 1), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), - BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_10, -16), + /* Limit r3 range to [1, 64] */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 63), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 1), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory region [1, 64] + * at &fp[-64] is not fully initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+32 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 3 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+32 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: 8 bytes no leak (init memory)", diff --git a/tools/testing/selftests/bpf/verifier/int_ptr.c b/tools/testing/selftests/bpf/verifier/int_ptr.c index 070893fb2900..02d9e004260b 100644 --- a/tools/testing/selftests/bpf/verifier/int_ptr.c +++ b/tools/testing/selftests/bpf/verifier/int_ptr.c @@ -54,12 +54,13 @@ /* bpf_strtoul() */ BPF_EMIT_CALL(BPF_FUNC_strtoul),
- BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .result = REJECT, - .prog_type = BPF_PROG_TYPE_CGROUP_SYSCTL, - .errstr = "invalid indirect read from stack R4 off -16+4 size 8", + .result_unpriv = REJECT, + .errstr_unpriv = "invalid indirect read from stack R4 off -16+4 size 8", + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "ARG_PTR_TO_LONG misaligned", diff --git a/tools/testing/selftests/bpf/verifier/search_pruning.c b/tools/testing/selftests/bpf/verifier/search_pruning.c index 7e36078f8f48..949cbe460248 100644 --- a/tools/testing/selftests/bpf/verifier/search_pruning.c +++ b/tools/testing/selftests/bpf/verifier/search_pruning.c @@ -128,9 +128,10 @@ BPF_EXIT_INSN(), }, .fixup_map_hash_8b = { 3 }, - .errstr = "invalid read from stack off -16+0 size 8", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .errstr_unpriv = "invalid read from stack off -16+0 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "allocated_stack", @@ -187,6 +188,8 @@ BPF_EXIT_INSN(), }, .flags = BPF_F_TEST_STATE_FREQ, - .errstr = "invalid read from stack off -8+1 size 8", - .result = REJECT, + .errstr_unpriv = "invalid read from stack off -8+1 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, diff --git a/tools/testing/selftests/bpf/verifier/sock.c b/tools/testing/selftests/bpf/verifier/sock.c index 8c224eac93df..59d976d22867 100644 --- a/tools/testing/selftests/bpf/verifier/sock.c +++ b/tools/testing/selftests/bpf/verifier/sock.c @@ -530,33 +530,6 @@ .prog_type = BPF_PROG_TYPE_SCHED_CLS, .result = ACCEPT, }, -{ - "sk_storage_get(map, skb->sk, &stack_value, 1): partially init stack_value", - .insns = { - BPF_MOV64_IMM(BPF_REG_2, 0), - BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), - BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)), - BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), - BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - BPF_MOV64_IMM(BPF_REG_4, 1), - BPF_MOV64_REG(BPF_REG_3, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -8), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_0), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_EMIT_CALL(BPF_FUNC_sk_storage_get), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .fixup_sk_storage_map = { 14 }, - .prog_type = BPF_PROG_TYPE_SCHED_CLS, - .result = REJECT, - .errstr = "invalid indirect read from stack", -}, { "bpf_map_lookup_elem(smap, &key)", .insns = { diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c index 0b943897aaf6..1e76841b7bfa 100644 --- a/tools/testing/selftests/bpf/verifier/spill_fill.c +++ b/tools/testing/selftests/bpf/verifier/spill_fill.c @@ -104,3 +104,214 @@ .result = ACCEPT, .retval = POINTER_VALUE, }, +{ + "Spill and refill a u32 const scalar. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u32 *)(r10 -8) */ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -8), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=20 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,off=20 R2=pkt R3=pkt_end R4=20 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,off=20,r=20 R2=pkt,r=20 R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill a u32 const, refill from another half of the uninit u32 from the stack", + .insns = { + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u32 *)(r10 -4) fp-8=????rrrr*/ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -4), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result_unpriv = REJECT, + .errstr_unpriv = "invalid read from stack off -4+0 size 4", + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, +}, +{ + "Spill a u32 const scalar. Refill as u16. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u16 *)(r10 -8) */ + BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_10, -8), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill u32 const scalars. Refill as u64. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r6 = 0 */ + BPF_MOV32_IMM(BPF_REG_6, 0), + /* r7 = 20 */ + BPF_MOV32_IMM(BPF_REG_7, 20), + /* *(u32 *)(r10 -4) = r6 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_6, -4), + /* *(u32 *)(r10 -8) = r7 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_7, -8), + /* r4 = *(u64 *)(r10 -8) */ + BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_10, -8), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill a u32 const scalar. Refill as u16 from fp-6. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u16 *)(r10 -6) */ + BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_10, -6), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill and refill a u32 const scalar at non 8byte aligned stack addr. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* *(u32 *)(r10 -4) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -4), + /* r4 = *(u32 *)(r10 -4), */ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -4), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=U32_MAX */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=U32_MAX R2=pkt R3=pkt_end R4= */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=U32_MAX R2=pkt R3=pkt_end R4= */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill and refill a umax=40 bounded scalar. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_1, + offsetof(struct __sk_buff, tstamp)), + BPF_JMP_IMM(BPF_JLE, BPF_REG_4, 40, 2), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + /* *(u32 *)(r10 -8) = r4 R4=umax=40 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = (*u32 *)(r10 - 8) */ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -8), + /* r2 += r4 R2=pkt R4=umax=40 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_4), + /* r0 = r2 R2=pkt,umax=40 R4=umax=40 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r2 += 20 R0=pkt,umax=40 R2=pkt,umax=40 */ + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 20), + /* if (r2 > r3) R0=pkt,umax=40 R2=pkt,off=20,umax=40 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_2, BPF_REG_3, 1), + /* r0 = *(u32 *)r0 R0=pkt,r=20,umax=40 R2=pkt,off=20,r=20,umax=40 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill a u32 scalar at fp-4 and then at fp-8", + .insns = { + /* r4 = 4321 */ + BPF_MOV32_IMM(BPF_REG_4, 4321), + /* *(u32 *)(r10 -4) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -4), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u64 *)(r10 -8) */ + BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, diff --git a/tools/testing/selftests/bpf/verifier/var_off.c b/tools/testing/selftests/bpf/verifier/var_off.c index eab1f7f56e2f..dc92a29f0d74 100644 --- a/tools/testing/selftests/bpf/verifier/var_off.c +++ b/tools/testing/selftests/bpf/verifier/var_off.c @@ -212,31 +212,6 @@ .result = REJECT, .prog_type = BPF_PROG_TYPE_LWT_IN, }, -{ - "indirect variable-offset stack access, max_off+size > max_initialized", - .insns = { - /* Fill only the second from top 8 bytes of the stack. */ - BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0), - /* Get an unknown value. */ - BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0), - /* Make it small and 4-byte aligned. */ - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4), - BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16), - /* Add it to fp. We now have either fp-12 or fp-16, but we don't know - * which. fp-12 size 8 is partially uninitialized stack. - */ - BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10), - /* Dereference it indirectly. */ - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .fixup_map_hash_8b = { 5 }, - .errstr = "invalid indirect read from stack R2 var_off", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_LWT_IN, -}, { "indirect variable-offset stack access, min_off < min_initialized", .insns = { @@ -289,33 +264,6 @@ .result = ACCEPT, .prog_type = BPF_PROG_TYPE_CGROUP_SKB, }, -{ - "indirect variable-offset stack access, uninitialized", - .insns = { - BPF_MOV64_IMM(BPF_REG_2, 6), - BPF_MOV64_IMM(BPF_REG_3, 28), - /* Fill the top 16 bytes of the stack. */ - BPF_ST_MEM(BPF_W, BPF_REG_10, -16, 0), - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - /* Get an unknown value. */ - BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1, 0), - /* Make it small and 4-byte aligned. */ - BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 4), - BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16), - /* Add it to fp. We now have either fp-12 or fp-16, we don't know - * which, but either way it points to initialized stack. - */ - BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_10), - BPF_MOV64_IMM(BPF_REG_5, 8), - /* Dereference it indirectly. */ - BPF_EMIT_CALL(BPF_FUNC_getsockopt), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .errstr = "invalid indirect read from stack R4 var_off", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_SOCK_OPS, -}, { "indirect variable-offset stack access, ok", .insns = {
From: Eduard Zingerman eddyz87@gmail.com
[ Upstream commit 6715df8d5d24655b9fd368e904028112b54c7de1 ]
This commits updates the following functions to allow reads from uninitialized stack locations when env->allow_uninit_stack option is enabled: - check_stack_read_fixed_off() - check_stack_range_initialized(), called from: - check_stack_read_var_off() - check_helper_mem_access()
Such change allows to relax logic in stacksafe() to treat STACK_MISC and STACK_INVALID in a same way and make the following stack slot configurations equivalent:
| Cached state | Current state | | stack slot | stack slot | |------------------+------------------| | STACK_INVALID or | STACK_INVALID or | | STACK_MISC | STACK_SPILL or | | | STACK_MISC or | | | STACK_ZERO or | | | STACK_DYNPTR |
This leads to significant verification speed gains (see below).
The idea was suggested by Andrii Nakryiko [1] and initial patch was created by Alexei Starovoitov [2].
Currently the env->allow_uninit_stack is allowed for programs loaded by users with CAP_PERFMON or CAP_SYS_ADMIN capabilities.
A number of test cases from verifier/*.c were expecting uninitialized stack access to be an error. These test cases were updated to execute in unprivileged mode (thus preserving the tests).
The test progs/test_global_func10.c expected "invalid indirect read from stack" error message because of the access to uninitialized memory region. This error is no longer possible in privileged mode. The test is updated to provoke an error "invalid indirect access to stack" because of access to invalid stack address (such error is not verified by progs/test_global_func*.c series of tests).
The following tests had to be removed because these can't be made unprivileged: - verifier/sock.c: - "sk_storage_get(map, skb->sk, &stack_value, 1): partially init stack_value" BPF_PROG_TYPE_SCHED_CLS programs are not executed in unprivileged mode. - verifier/var_off.c: - "indirect variable-offset stack access, max_off+size > max_initialized" - "indirect variable-offset stack access, uninitialized" These tests verify that access to uninitialized stack values is detected when stack offset is not a constant. However, variable stack access is prohibited in unprivileged mode, thus these tests are no longer valid.
* * *
Here is veristat log comparing this patch with current master on a set of selftest binaries listed in tools/testing/selftests/bpf/veristat.cfg and cilium BPF binaries (see [3]):
$ ./veristat -e file,prog,states -C -f 'states_pct<-30' master.log current.log File Program States (A) States (B) States (DIFF) -------------------------- -------------------------- ---------- ---------- ---------------- bpf_host.o tail_handle_ipv6_from_host 349 244 -105 (-30.09%) bpf_host.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_lxc.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_sock.o cil_sock4_connect 70 48 -22 (-31.43%) bpf_sock.o cil_sock4_sendmsg 68 46 -22 (-32.35%) bpf_xdp.o tail_handle_nat_fwd_ipv4 1554 803 -751 (-48.33%) bpf_xdp.o tail_lb_ipv4 6457 2473 -3984 (-61.70%) bpf_xdp.o tail_lb_ipv6 7249 3908 -3341 (-46.09%) pyperf600_bpf_loop.bpf.o on_event 287 145 -142 (-49.48%) strobemeta.bpf.o on_event 15915 4772 -11143 (-70.02%) strobemeta_nounroll2.bpf.o on_event 17087 3820 -13267 (-77.64%) xdp_synproxy_kern.bpf.o syncookie_tc 21271 6635 -14636 (-68.81%) xdp_synproxy_kern.bpf.o syncookie_xdp 23122 6024 -17098 (-73.95%) -------------------------- -------------------------- ---------- ---------- ----------------
Note: I limited selection by states_pct<-30%.
Inspection of differences in pyperf600_bpf_loop behavior shows that the following patch for the test removes almost all differences:
- a/tools/testing/selftests/bpf/progs/pyperf.h + b/tools/testing/selftests/bpf/progs/pyperf.h @ -266,8 +266,8 @ int __on_event(struct bpf_raw_tracepoint_args *ctx) }
if (event->pthread_match || !pidData->use_tls) { - void* frame_ptr; - FrameData frame; + void* frame_ptr = 0; + FrameData frame = {}; Symbol sym = {}; int cur_cpu = bpf_get_smp_processor_id();
W/o this patch the difference comes from the following pattern (for different variables):
static bool get_frame_data(... FrameData *frame ...) { ... bpf_probe_read_user(&frame->f_code, ...); if (!frame->f_code) return false; ... bpf_probe_read_user(&frame->co_name, ...); if (frame->co_name) ...; }
int __on_event(struct bpf_raw_tracepoint_args *ctx) { FrameData frame; ... get_frame_data(... &frame ...) // indirectly via a bpf_loop & callback ... }
SEC("raw_tracepoint/kfree_skb") int on_event(struct bpf_raw_tracepoint_args* ctx) { ... ret |= __on_event(ctx); ret |= __on_event(ctx); ... }
With regards to value `frame->co_name` the following is important: - Because of the conditional `if (!frame->f_code)` each call to __on_event() produces two states, one with `frame->co_name` marked as STACK_MISC, another with it as is (and marked STACK_INVALID on a first call). - The call to bpf_probe_read_user() does not mark stack slots corresponding to `&frame->co_name` as REG_LIVE_WRITTEN but it marks these slots as BPF_MISC, this happens because of the following loop in the check_helper_call():
for (i = 0; i < meta.access_size; i++) { err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1, false); if (err) return err; }
Note the size of the write, it is a one byte write for each byte touched by a helper. The BPF_B write does not lead to write marks for the target stack slot. - Which means that w/o this patch when second __on_event() call is verified `if (frame->co_name)` will propagate read marks first to a stack slot with STACK_MISC marks and second to a stack slot with STACK_INVALID marks and these states would be considered different.
[1] https://lore.kernel.org/bpf/CAEf4BzY3e+ZuC6HUa8dCiUovQRg2SzEk7M-dSkqNZyn=xEm... [2] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu... [3] git@github.com:anakryiko/cilium.git
Suggested-by: Andrii Nakryiko andrii@kernel.org Co-developed-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Eduard Zingerman eddyz87@gmail.com Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20230219200427.606541-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Maxim Mikityanskiy maxim@isovalent.com --- Backporting to address the complexity regression introduced by commit 71f656a50176 ("bpf: Fix to preserve reg parent/live fields when copying range info"), that affects Cilium built with LLVM 18.
kernel/bpf/verifier.c | 11 +- .../selftests/bpf/progs/test_global_func10.c | 9 +- tools/testing/selftests/bpf/verifier/calls.c | 13 +- .../bpf/verifier/helper_access_var_len.c | 104 ++++++--- .../testing/selftests/bpf/verifier/int_ptr.c | 9 +- .../selftests/bpf/verifier/search_pruning.c | 13 +- tools/testing/selftests/bpf/verifier/sock.c | 27 --- .../selftests/bpf/verifier/spill_fill.c | 211 ++++++++++++++++++ .../testing/selftests/bpf/verifier/var_off.c | 52 ----- 9 files changed, 316 insertions(+), 133 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b9f63c4b8598..88b38db5f626 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3159,6 +3159,8 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, continue; if (type == STACK_MISC) continue; + if (type == STACK_INVALID && env->allow_uninit_stack) + continue; verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -3196,6 +3198,8 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, continue; if (type == STACK_ZERO) continue; + if (type == STACK_INVALID && env->allow_uninit_stack) + continue; verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -4782,7 +4786,8 @@ static int check_stack_range_initialized( stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; if (*stype == STACK_MISC) goto mark; - if (*stype == STACK_ZERO) { + if ((*stype == STACK_ZERO) || + (*stype == STACK_INVALID && env->allow_uninit_stack)) { if (clobber) { /* helper can write anything into the stack */ *stype = STACK_MISC; @@ -10625,6 +10630,10 @@ static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old, if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID) continue;
+ if (env->allow_uninit_stack && + old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_MISC) + continue; + /* explored stack has more populated slots than current stack * and these slots were used */ diff --git a/tools/testing/selftests/bpf/progs/test_global_func10.c b/tools/testing/selftests/bpf/progs/test_global_func10.c index 97b7031d0e22..d361eba167f6 100644 --- a/tools/testing/selftests/bpf/progs/test_global_func10.c +++ b/tools/testing/selftests/bpf/progs/test_global_func10.c @@ -4,12 +4,12 @@ #include <bpf/bpf_helpers.h>
struct Small { - int x; + long x; };
struct Big { - int x; - int y; + long x; + long y; };
__noinline int foo(const struct Big *big) @@ -21,7 +21,8 @@ __noinline int foo(const struct Big *big) }
SEC("cgroup_skb/ingress") -int test_cls(struct __sk_buff *skb) +__failure __msg("invalid indirect access to stack") +int global_func10(struct __sk_buff *skb) { const struct Small small = {.x = skb->len };
diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c index 2e701e7f6968..5d1e01d54a82 100644 --- a/tools/testing/selftests/bpf/verifier/calls.c +++ b/tools/testing/selftests/bpf/verifier/calls.c @@ -1967,19 +1967,22 @@ * that fp-8 stack slot was unused in the fall-through * branch and will accept the program incorrectly */ - BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 2, 2), + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_JMP_IMM(BPF_JGT, BPF_REG_0, 2, 2), BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_JMP_IMM(BPF_JA, 0, 0, 0), BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), BPF_LD_MAP_FD(BPF_REG_1, 0), BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .fixup_map_hash_48b = { 6 }, - .errstr = "invalid indirect read from stack R2 off -8+0 size 8", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_XDP, + .fixup_map_hash_48b = { 7 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -8+0 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "calls: ctx read at start of subprog", diff --git a/tools/testing/selftests/bpf/verifier/helper_access_var_len.c b/tools/testing/selftests/bpf/verifier/helper_access_var_len.c index 0ab7f1dfc97a..0e24aa11c457 100644 --- a/tools/testing/selftests/bpf/verifier/helper_access_var_len.c +++ b/tools/testing/selftests/bpf/verifier/helper_access_var_len.c @@ -29,19 +29,30 @@ { "helper access to variable memory: stack, bitwise AND, zero included", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, -128), - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 64), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + /* use bitwise AND to limit r3 range to [0, 64] */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 64), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory at &fp[-64] is + * not initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+0 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 4 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+0 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: stack, bitwise AND + JMP, wrong max", @@ -183,20 +194,31 @@ { "helper access to variable memory: stack, JMP, no min check", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, -128), - BPF_JMP_IMM(BPF_JGT, BPF_REG_2, 64, 3), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + /* use JMP to limit r3 range to [0, 64] */ + BPF_JMP_IMM(BPF_JGT, BPF_REG_3, 64, 6), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory at &fp[-64] is + * not initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+0 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 4 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+0 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: stack, JMP (signed), no min check", @@ -564,29 +586,41 @@ { "helper access to variable memory: 8 bytes leak", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -64), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -56), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -48), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -40), + /* Note: fp[-32] left uninitialized */ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -24), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -16), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8), - BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, -128), - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 63), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 1), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), - BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_10, -16), + /* Limit r3 range to [1, 64] */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 63), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 1), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory region [1, 64] + * at &fp[-64] is not fully initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+32 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 3 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+32 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: 8 bytes no leak (init memory)", diff --git a/tools/testing/selftests/bpf/verifier/int_ptr.c b/tools/testing/selftests/bpf/verifier/int_ptr.c index 070893fb2900..02d9e004260b 100644 --- a/tools/testing/selftests/bpf/verifier/int_ptr.c +++ b/tools/testing/selftests/bpf/verifier/int_ptr.c @@ -54,12 +54,13 @@ /* bpf_strtoul() */ BPF_EMIT_CALL(BPF_FUNC_strtoul),
- BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .result = REJECT, - .prog_type = BPF_PROG_TYPE_CGROUP_SYSCTL, - .errstr = "invalid indirect read from stack R4 off -16+4 size 8", + .result_unpriv = REJECT, + .errstr_unpriv = "invalid indirect read from stack R4 off -16+4 size 8", + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "ARG_PTR_TO_LONG misaligned", diff --git a/tools/testing/selftests/bpf/verifier/search_pruning.c b/tools/testing/selftests/bpf/verifier/search_pruning.c index 7e36078f8f48..949cbe460248 100644 --- a/tools/testing/selftests/bpf/verifier/search_pruning.c +++ b/tools/testing/selftests/bpf/verifier/search_pruning.c @@ -128,9 +128,10 @@ BPF_EXIT_INSN(), }, .fixup_map_hash_8b = { 3 }, - .errstr = "invalid read from stack off -16+0 size 8", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .errstr_unpriv = "invalid read from stack off -16+0 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "allocated_stack", @@ -187,6 +188,8 @@ BPF_EXIT_INSN(), }, .flags = BPF_F_TEST_STATE_FREQ, - .errstr = "invalid read from stack off -8+1 size 8", - .result = REJECT, + .errstr_unpriv = "invalid read from stack off -8+1 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, diff --git a/tools/testing/selftests/bpf/verifier/sock.c b/tools/testing/selftests/bpf/verifier/sock.c index 8c224eac93df..59d976d22867 100644 --- a/tools/testing/selftests/bpf/verifier/sock.c +++ b/tools/testing/selftests/bpf/verifier/sock.c @@ -530,33 +530,6 @@ .prog_type = BPF_PROG_TYPE_SCHED_CLS, .result = ACCEPT, }, -{ - "sk_storage_get(map, skb->sk, &stack_value, 1): partially init stack_value", - .insns = { - BPF_MOV64_IMM(BPF_REG_2, 0), - BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), - BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)), - BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), - BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - BPF_MOV64_IMM(BPF_REG_4, 1), - BPF_MOV64_REG(BPF_REG_3, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -8), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_0), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_EMIT_CALL(BPF_FUNC_sk_storage_get), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .fixup_sk_storage_map = { 14 }, - .prog_type = BPF_PROG_TYPE_SCHED_CLS, - .result = REJECT, - .errstr = "invalid indirect read from stack", -}, { "bpf_map_lookup_elem(smap, &key)", .insns = { diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c index 0b943897aaf6..1e76841b7bfa 100644 --- a/tools/testing/selftests/bpf/verifier/spill_fill.c +++ b/tools/testing/selftests/bpf/verifier/spill_fill.c @@ -104,3 +104,214 @@ .result = ACCEPT, .retval = POINTER_VALUE, }, +{ + "Spill and refill a u32 const scalar. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u32 *)(r10 -8) */ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -8), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=20 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,off=20 R2=pkt R3=pkt_end R4=20 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,off=20,r=20 R2=pkt,r=20 R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill a u32 const, refill from another half of the uninit u32 from the stack", + .insns = { + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u32 *)(r10 -4) fp-8=????rrrr*/ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -4), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result_unpriv = REJECT, + .errstr_unpriv = "invalid read from stack off -4+0 size 4", + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, +}, +{ + "Spill a u32 const scalar. Refill as u16. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u16 *)(r10 -8) */ + BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_10, -8), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill u32 const scalars. Refill as u64. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r6 = 0 */ + BPF_MOV32_IMM(BPF_REG_6, 0), + /* r7 = 20 */ + BPF_MOV32_IMM(BPF_REG_7, 20), + /* *(u32 *)(r10 -4) = r6 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_6, -4), + /* *(u32 *)(r10 -8) = r7 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_7, -8), + /* r4 = *(u64 *)(r10 -8) */ + BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_10, -8), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill a u32 const scalar. Refill as u16 from fp-6. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u16 *)(r10 -6) */ + BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_10, -6), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill and refill a u32 const scalar at non 8byte aligned stack addr. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + /* r4 = 20 */ + BPF_MOV32_IMM(BPF_REG_4, 20), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* *(u32 *)(r10 -4) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -4), + /* r4 = *(u32 *)(r10 -4), */ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -4), + /* r0 = r2 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=U32_MAX */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4), + /* if (r0 > r3) R0=pkt,umax=U32_MAX R2=pkt R3=pkt_end R4= */ + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + /* r0 = *(u32 *)r2 R0=pkt,umax=U32_MAX R2=pkt R3=pkt_end R4= */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "invalid access to packet", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill and refill a umax=40 bounded scalar. Offset to skb->data", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_1, + offsetof(struct __sk_buff, tstamp)), + BPF_JMP_IMM(BPF_JLE, BPF_REG_4, 40, 2), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + /* *(u32 *)(r10 -8) = r4 R4=umax=40 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = (*u32 *)(r10 - 8) */ + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_10, -8), + /* r2 += r4 R2=pkt R4=umax=40 */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_4), + /* r0 = r2 R2=pkt,umax=40 R4=umax=40 */ + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + /* r2 += 20 R0=pkt,umax=40 R2=pkt,umax=40 */ + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 20), + /* if (r2 > r3) R0=pkt,umax=40 R2=pkt,off=20,umax=40 */ + BPF_JMP_REG(BPF_JGT, BPF_REG_2, BPF_REG_3, 1), + /* r0 = *(u32 *)r0 R0=pkt,r=20,umax=40 R2=pkt,off=20,r=20,umax=40 */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, +{ + "Spill a u32 scalar at fp-4 and then at fp-8", + .insns = { + /* r4 = 4321 */ + BPF_MOV32_IMM(BPF_REG_4, 4321), + /* *(u32 *)(r10 -4) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -4), + /* *(u32 *)(r10 -8) = r4 */ + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8), + /* r4 = *(u64 *)(r10 -8) */ + BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, diff --git a/tools/testing/selftests/bpf/verifier/var_off.c b/tools/testing/selftests/bpf/verifier/var_off.c index eab1f7f56e2f..dc92a29f0d74 100644 --- a/tools/testing/selftests/bpf/verifier/var_off.c +++ b/tools/testing/selftests/bpf/verifier/var_off.c @@ -212,31 +212,6 @@ .result = REJECT, .prog_type = BPF_PROG_TYPE_LWT_IN, }, -{ - "indirect variable-offset stack access, max_off+size > max_initialized", - .insns = { - /* Fill only the second from top 8 bytes of the stack. */ - BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0), - /* Get an unknown value. */ - BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0), - /* Make it small and 4-byte aligned. */ - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4), - BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16), - /* Add it to fp. We now have either fp-12 or fp-16, but we don't know - * which. fp-12 size 8 is partially uninitialized stack. - */ - BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10), - /* Dereference it indirectly. */ - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .fixup_map_hash_8b = { 5 }, - .errstr = "invalid indirect read from stack R2 var_off", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_LWT_IN, -}, { "indirect variable-offset stack access, min_off < min_initialized", .insns = { @@ -289,33 +264,6 @@ .result = ACCEPT, .prog_type = BPF_PROG_TYPE_CGROUP_SKB, }, -{ - "indirect variable-offset stack access, uninitialized", - .insns = { - BPF_MOV64_IMM(BPF_REG_2, 6), - BPF_MOV64_IMM(BPF_REG_3, 28), - /* Fill the top 16 bytes of the stack. */ - BPF_ST_MEM(BPF_W, BPF_REG_10, -16, 0), - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - /* Get an unknown value. */ - BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1, 0), - /* Make it small and 4-byte aligned. */ - BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 4), - BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16), - /* Add it to fp. We now have either fp-12 or fp-16, we don't know - * which, but either way it points to initialized stack. - */ - BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_10), - BPF_MOV64_IMM(BPF_REG_5, 8), - /* Dereference it indirectly. */ - BPF_EMIT_CALL(BPF_FUNC_getsockopt), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .errstr = "invalid indirect read from stack R4 var_off", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_SOCK_OPS, -}, { "indirect variable-offset stack access, ok", .insns = {
Hi All,
We found BPF sefltest fail to build with following error:
08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:1: error: unknown type name '__failure' 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:17: error: expected parameter declarator 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:17: error: expected ')' 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:16: note: to match this '(' 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:52: error: expected ';' after top level declarator 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: ; 08-09 20:39:59 DBG: |output|: 4 errors generated. 08-09 20:39:59 DBG: |output|: make: *** [Makefile:470: /root/oltf/work/linux-bpf-qa/tools/testing/selftests/bpf/test_global_func10.o] Error 1 08-09 20:39:59 DBG: |output|: make: *** Waiting for unfinished jobs....
It happens from the commit e30bc19a9ee8("bpf: Allow reads from uninit stack"). We did a further look, '__failure' is defined in tools/testing/selftests/bpf/progs/bpf_misc.h, and was 1st introduced in commit 537c3f66eac1("selftests/bpf: add generic BPF program tester-loader") which is not backported to linux-5.15.y.
So we may need to revert the patch, or fix it.
Kind regards, Sherry
On Thu, Aug 22, 2024 at 06:45:14PM GMT, Sherry Yang wrote:
Hi All,
We found BPF sefltest fail to build with following error:
08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:1: error: unknown type name '__failure' 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:17: error: expected parameter declarator 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:17: error: expected ')' 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:16: note: to match this '(' 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:52: error: expected ';' after top level declarator 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: ; 08-09 20:39:59 DBG: |output|: 4 errors generated. 08-09 20:39:59 DBG: |output|: make: *** [Makefile:470: /root/oltf/work/linux-bpf-qa/tools/testing/selftests/bpf/test_global_func10.o] Error 1 08-09 20:39:59 DBG: |output|: make: *** Waiting for unfinished jobs....
It happens from the commit e30bc19a9ee8("bpf: Allow reads from uninit stack"). We did a further look, '__failure' is defined in tools/testing/selftests/bpf/progs/bpf_misc.h, and was 1st introduced in commit 537c3f66eac1("selftests/bpf: add generic BPF program tester-loader") which is not backported to linux-5.15.y.
So we may need to revert the patch, or fix it.
To fix it I think we just need to drop the use of __failure and __msg in progs/test_global_func10.c, and update the "struct test_def tests[]" table in prog_tests/test_global_funcs.c with the new verifier rejection message.
On the other hand I believe commit 537c3f66eac1("selftests/bpf: add generic BPF program tester-loader") should be relatively easy to backport, just picking that commit up and resolving simple conflict in Makefile should be enough. It will also save a lot of future headaches like this one.
(Note: the generic test-loader patch will need to backport it to stable 6.1 first before it an be backported to 5.15, as per the stable rule[1])
1: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#proc...
On Fri, Aug 23, 2024 at 10:50:29AM +0800, Shung-Hsi Yu wrote:
On Thu, Aug 22, 2024 at 06:45:14PM GMT, Sherry Yang wrote:
Hi All,
We found BPF sefltest fail to build with following error:
08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:1: error: unknown type name '__failure' 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:17: error: expected parameter declarator 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:17: error: expected ')' 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:16: note: to match this '(' 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: progs/test_global_func10.c:24:52: error: expected ';' after top level declarator 08-09 20:39:59 DBG: |output|: __failure __msg("invalid indirect access to stack") 08-09 20:39:59 DBG: |output|: ^ 08-09 20:39:59 DBG: |output|: ; 08-09 20:39:59 DBG: |output|: 4 errors generated. 08-09 20:39:59 DBG: |output|: make: *** [Makefile:470: /root/oltf/work/linux-bpf-qa/tools/testing/selftests/bpf/test_global_func10.o] Error 1 08-09 20:39:59 DBG: |output|: make: *** Waiting for unfinished jobs....
It happens from the commit e30bc19a9ee8("bpf: Allow reads from uninit stack"). We did a further look, '__failure' is defined in tools/testing/selftests/bpf/progs/bpf_misc.h, and was 1st introduced in commit 537c3f66eac1("selftests/bpf: add generic BPF program tester-loader") which is not backported to linux-5.15.y.
So we may need to revert the patch, or fix it.
To fix it I think we just need to drop the use of __failure and __msg in progs/test_global_func10.c, and update the "struct test_def tests[]" table in prog_tests/test_global_funcs.c with the new verifier rejection message.
On the other hand I believe commit 537c3f66eac1("selftests/bpf: add generic BPF program tester-loader") should be relatively easy to backport, just picking that commit up and resolving simple conflict in Makefile should be enough. It will also save a lot of future headaches like this one.
Please submit a patch like this and we will be glad to pick it up.
thanks,
greg k-h
From: Eduard Zingerman eddyz87@gmail.com
[ Upstream commit 6715df8d5d24655b9fd368e904028112b54c7de1 ]
This commits updates the following functions to allow reads from uninitialized stack locations when env->allow_uninit_stack option is enabled: - check_stack_read_fixed_off() - check_stack_range_initialized(), called from: - check_stack_read_var_off() - check_helper_mem_access()
Such change allows to relax logic in stacksafe() to treat STACK_MISC and STACK_INVALID in a same way and make the following stack slot configurations equivalent:
| Cached state | Current state | | stack slot | stack slot | |------------------+------------------| | STACK_INVALID or | STACK_INVALID or | | STACK_MISC | STACK_SPILL or | | | STACK_MISC or | | | STACK_ZERO or | | | STACK_DYNPTR |
This leads to significant verification speed gains (see below).
The idea was suggested by Andrii Nakryiko [1] and initial patch was created by Alexei Starovoitov [2].
Currently the env->allow_uninit_stack is allowed for programs loaded by users with CAP_PERFMON or CAP_SYS_ADMIN capabilities.
A number of test cases from verifier/*.c were expecting uninitialized stack access to be an error. These test cases were updated to execute in unprivileged mode (thus preserving the tests).
The test progs/test_global_func10.c expected "invalid indirect read from stack" error message because of the access to uninitialized memory region. This error is no longer possible in privileged mode. The test is updated to provoke an error "invalid indirect access to stack" because of access to invalid stack address (such error is not verified by progs/test_global_func*.c series of tests).
The following tests had to be removed because these can't be made unprivileged: - verifier/sock.c: - "sk_storage_get(map, skb->sk, &stack_value, 1): partially init stack_value" BPF_PROG_TYPE_SCHED_CLS programs are not executed in unprivileged mode. - verifier/var_off.c: - "indirect variable-offset stack access, max_off+size > max_initialized" - "indirect variable-offset stack access, uninitialized" These tests verify that access to uninitialized stack values is detected when stack offset is not a constant. However, variable stack access is prohibited in unprivileged mode, thus these tests are no longer valid.
* * *
Here is veristat log comparing this patch with current master on a set of selftest binaries listed in tools/testing/selftests/bpf/veristat.cfg and cilium BPF binaries (see [3]):
$ ./veristat -e file,prog,states -C -f 'states_pct<-30' master.log current.log File Program States (A) States (B) States (DIFF) -------------------------- -------------------------- ---------- ---------- ---------------- bpf_host.o tail_handle_ipv6_from_host 349 244 -105 (-30.09%) bpf_host.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_lxc.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_sock.o cil_sock4_connect 70 48 -22 (-31.43%) bpf_sock.o cil_sock4_sendmsg 68 46 -22 (-32.35%) bpf_xdp.o tail_handle_nat_fwd_ipv4 1554 803 -751 (-48.33%) bpf_xdp.o tail_lb_ipv4 6457 2473 -3984 (-61.70%) bpf_xdp.o tail_lb_ipv6 7249 3908 -3341 (-46.09%) pyperf600_bpf_loop.bpf.o on_event 287 145 -142 (-49.48%) strobemeta.bpf.o on_event 15915 4772 -11143 (-70.02%) strobemeta_nounroll2.bpf.o on_event 17087 3820 -13267 (-77.64%) xdp_synproxy_kern.bpf.o syncookie_tc 21271 6635 -14636 (-68.81%) xdp_synproxy_kern.bpf.o syncookie_xdp 23122 6024 -17098 (-73.95%) -------------------------- -------------------------- ---------- ---------- ----------------
Note: I limited selection by states_pct<-30%.
Inspection of differences in pyperf600_bpf_loop behavior shows that the following patch for the test removes almost all differences:
- a/tools/testing/selftests/bpf/progs/pyperf.h + b/tools/testing/selftests/bpf/progs/pyperf.h @ -266,8 +266,8 @ int __on_event(struct bpf_raw_tracepoint_args *ctx) }
if (event->pthread_match || !pidData->use_tls) { - void* frame_ptr; - FrameData frame; + void* frame_ptr = 0; + FrameData frame = {}; Symbol sym = {}; int cur_cpu = bpf_get_smp_processor_id();
W/o this patch the difference comes from the following pattern (for different variables):
static bool get_frame_data(... FrameData *frame ...) { ... bpf_probe_read_user(&frame->f_code, ...); if (!frame->f_code) return false; ... bpf_probe_read_user(&frame->co_name, ...); if (frame->co_name) ...; }
int __on_event(struct bpf_raw_tracepoint_args *ctx) { FrameData frame; ... get_frame_data(... &frame ...) // indirectly via a bpf_loop & callback ... }
SEC("raw_tracepoint/kfree_skb") int on_event(struct bpf_raw_tracepoint_args* ctx) { ... ret |= __on_event(ctx); ret |= __on_event(ctx); ... }
With regards to value `frame->co_name` the following is important: - Because of the conditional `if (!frame->f_code)` each call to __on_event() produces two states, one with `frame->co_name` marked as STACK_MISC, another with it as is (and marked STACK_INVALID on a first call). - The call to bpf_probe_read_user() does not mark stack slots corresponding to `&frame->co_name` as REG_LIVE_WRITTEN but it marks these slots as BPF_MISC, this happens because of the following loop in the check_helper_call():
for (i = 0; i < meta.access_size; i++) { err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1, false); if (err) return err; }
Note the size of the write, it is a one byte write for each byte touched by a helper. The BPF_B write does not lead to write marks for the target stack slot. - Which means that w/o this patch when second __on_event() call is verified `if (frame->co_name)` will propagate read marks first to a stack slot with STACK_MISC marks and second to a stack slot with STACK_INVALID marks and these states would be considered different.
[1] https://lore.kernel.org/bpf/CAEf4BzY3e+ZuC6HUa8dCiUovQRg2SzEk7M-dSkqNZyn=xEm... [2] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu... [3] git@github.com:anakryiko/cilium.git
Suggested-by: Andrii Nakryiko andrii@kernel.org Co-developed-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Eduard Zingerman eddyz87@gmail.com Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20230219200427.606541-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Maxim Mikityanskiy maxim@isovalent.com --- Backporting to address the complexity regression introduced by commit 71f656a50176 ("bpf: Fix to preserve reg parent/live fields when copying range info"), that affects Cilium built with LLVM 18.
kernel/bpf/verifier.c | 11 +- .../selftests/bpf/progs/test_global_func10.c | 9 +- tools/testing/selftests/bpf/verifier/calls.c | 13 ++- .../bpf/verifier/helper_access_var_len.c | 104 ++++++++++++------ .../testing/selftests/bpf/verifier/int_ptr.c | 9 +- .../selftests/bpf/verifier/search_pruning.c | 13 ++- tools/testing/selftests/bpf/verifier/sock.c | 27 ----- .../selftests/bpf/verifier/spill_fill.c | 7 +- .../testing/selftests/bpf/verifier/var_off.c | 52 --------- 9 files changed, 109 insertions(+), 136 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 56a5c8beb553..8973d3c9597c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3599,6 +3599,8 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, continue; if (type == STACK_MISC) continue; + if (type == STACK_INVALID && env->allow_uninit_stack) + continue; verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -3636,6 +3638,8 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, continue; if (type == STACK_ZERO) continue; + if (type == STACK_INVALID && env->allow_uninit_stack) + continue; verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -5426,7 +5430,8 @@ static int check_stack_range_initialized( stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; if (*stype == STACK_MISC) goto mark; - if (*stype == STACK_ZERO) { + if ((*stype == STACK_ZERO) || + (*stype == STACK_INVALID && env->allow_uninit_stack)) { if (clobber) { /* helper can write anything into the stack */ *stype = STACK_MISC; @@ -11967,6 +11972,10 @@ static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old, if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID) continue;
+ if (env->allow_uninit_stack && + old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_MISC) + continue; + /* explored stack has more populated slots than current stack * and these slots were used */ diff --git a/tools/testing/selftests/bpf/progs/test_global_func10.c b/tools/testing/selftests/bpf/progs/test_global_func10.c index 97b7031d0e22..d361eba167f6 100644 --- a/tools/testing/selftests/bpf/progs/test_global_func10.c +++ b/tools/testing/selftests/bpf/progs/test_global_func10.c @@ -4,12 +4,12 @@ #include <bpf/bpf_helpers.h>
struct Small { - int x; + long x; };
struct Big { - int x; - int y; + long x; + long y; };
__noinline int foo(const struct Big *big) @@ -21,7 +21,8 @@ __noinline int foo(const struct Big *big) }
SEC("cgroup_skb/ingress") -int test_cls(struct __sk_buff *skb) +__failure __msg("invalid indirect access to stack") +int global_func10(struct __sk_buff *skb) { const struct Small small = {.x = skb->len };
diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c index e1a937277b54..a201d2871bfb 100644 --- a/tools/testing/selftests/bpf/verifier/calls.c +++ b/tools/testing/selftests/bpf/verifier/calls.c @@ -2221,19 +2221,22 @@ * that fp-8 stack slot was unused in the fall-through * branch and will accept the program incorrectly */ - BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 2, 2), + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_JMP_IMM(BPF_JGT, BPF_REG_0, 2, 2), BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_JMP_IMM(BPF_JA, 0, 0, 0), BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), BPF_LD_MAP_FD(BPF_REG_1, 0), BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .fixup_map_hash_48b = { 6 }, - .errstr = "invalid indirect read from stack R2 off -8+0 size 8", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_XDP, + .fixup_map_hash_48b = { 7 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -8+0 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "calls: ctx read at start of subprog", diff --git a/tools/testing/selftests/bpf/verifier/helper_access_var_len.c b/tools/testing/selftests/bpf/verifier/helper_access_var_len.c index a6c869a7319c..9c4885885aba 100644 --- a/tools/testing/selftests/bpf/verifier/helper_access_var_len.c +++ b/tools/testing/selftests/bpf/verifier/helper_access_var_len.c @@ -29,19 +29,30 @@ { "helper access to variable memory: stack, bitwise AND, zero included", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, -128), - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 64), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + /* use bitwise AND to limit r3 range to [0, 64] */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 64), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory at &fp[-64] is + * not initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+0 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 4 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+0 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: stack, bitwise AND + JMP, wrong max", @@ -183,20 +194,31 @@ { "helper access to variable memory: stack, JMP, no min check", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, -128), - BPF_JMP_IMM(BPF_JGT, BPF_REG_2, 64, 3), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + /* use JMP to limit r3 range to [0, 64] */ + BPF_JMP_IMM(BPF_JGT, BPF_REG_3, 64, 6), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory at &fp[-64] is + * not initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+0 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 4 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+0 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: stack, JMP (signed), no min check", @@ -564,29 +586,41 @@ { "helper access to variable memory: 8 bytes leak", .insns = { - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 8), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -64), + /* set max stack size */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -128, 0), + /* set r3 to a random value */ + BPF_EMIT_CALL(BPF_FUNC_get_prandom_u32), + BPF_MOV64_REG(BPF_REG_3, BPF_REG_0), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -64), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -64), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -56), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -48), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -40), + /* Note: fp[-32] left uninitialized */ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -24), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -16), BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8), - BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -128), - BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, -128), - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 63), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 1), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel), - BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_10, -16), + /* Limit r3 range to [1, 64] */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 63), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 1), + BPF_MOV64_IMM(BPF_REG_4, 0), + /* Call bpf_ringbuf_output(), it is one of a few helper functions with + * ARG_CONST_SIZE_OR_ZERO parameter allowed in unpriv mode. + * For unpriv this should signal an error, because memory region [1, 64] + * at &fp[-64] is not fully initialized. + */ + BPF_EMIT_CALL(BPF_FUNC_ringbuf_output), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .errstr = "invalid indirect read from stack R1 off -64+32 size 64", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .fixup_map_ringbuf = { 3 }, + .errstr_unpriv = "invalid indirect read from stack R2 off -64+32 size 64", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "helper access to variable memory: 8 bytes no leak (init memory)", diff --git a/tools/testing/selftests/bpf/verifier/int_ptr.c b/tools/testing/selftests/bpf/verifier/int_ptr.c index 070893fb2900..02d9e004260b 100644 --- a/tools/testing/selftests/bpf/verifier/int_ptr.c +++ b/tools/testing/selftests/bpf/verifier/int_ptr.c @@ -54,12 +54,13 @@ /* bpf_strtoul() */ BPF_EMIT_CALL(BPF_FUNC_strtoul),
- BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .result = REJECT, - .prog_type = BPF_PROG_TYPE_CGROUP_SYSCTL, - .errstr = "invalid indirect read from stack R4 off -16+4 size 8", + .result_unpriv = REJECT, + .errstr_unpriv = "invalid indirect read from stack R4 off -16+4 size 8", + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "ARG_PTR_TO_LONG misaligned", diff --git a/tools/testing/selftests/bpf/verifier/search_pruning.c b/tools/testing/selftests/bpf/verifier/search_pruning.c index d63fd8991b03..745d6b5842fd 100644 --- a/tools/testing/selftests/bpf/verifier/search_pruning.c +++ b/tools/testing/selftests/bpf/verifier/search_pruning.c @@ -128,9 +128,10 @@ BPF_EXIT_INSN(), }, .fixup_map_hash_8b = { 3 }, - .errstr = "invalid read from stack off -16+0 size 8", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_TRACEPOINT, + .errstr_unpriv = "invalid read from stack off -16+0 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "precision tracking for u32 spill/fill", @@ -258,6 +259,8 @@ BPF_EXIT_INSN(), }, .flags = BPF_F_TEST_STATE_FREQ, - .errstr = "invalid read from stack off -8+1 size 8", - .result = REJECT, + .errstr_unpriv = "invalid read from stack off -8+1 size 8", + .result_unpriv = REJECT, + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, diff --git a/tools/testing/selftests/bpf/verifier/sock.c b/tools/testing/selftests/bpf/verifier/sock.c index d11d0b28be41..108dd3ee1edd 100644 --- a/tools/testing/selftests/bpf/verifier/sock.c +++ b/tools/testing/selftests/bpf/verifier/sock.c @@ -530,33 +530,6 @@ .prog_type = BPF_PROG_TYPE_SCHED_CLS, .result = ACCEPT, }, -{ - "sk_storage_get(map, skb->sk, &stack_value, 1): partially init stack_value", - .insns = { - BPF_MOV64_IMM(BPF_REG_2, 0), - BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), - BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)), - BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), - BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - BPF_MOV64_IMM(BPF_REG_4, 1), - BPF_MOV64_REG(BPF_REG_3, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -8), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_0), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_EMIT_CALL(BPF_FUNC_sk_storage_get), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .fixup_sk_storage_map = { 14 }, - .prog_type = BPF_PROG_TYPE_SCHED_CLS, - .result = REJECT, - .errstr = "invalid indirect read from stack", -}, { "bpf_map_lookup_elem(smap, &key)", .insns = { diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c index e23f07175e1b..53286a7b49aa 100644 --- a/tools/testing/selftests/bpf/verifier/spill_fill.c +++ b/tools/testing/selftests/bpf/verifier/spill_fill.c @@ -171,9 +171,10 @@ BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, - .result = REJECT, - .errstr = "invalid read from stack off -4+0 size 4", - .prog_type = BPF_PROG_TYPE_SCHED_CLS, + .result_unpriv = REJECT, + .errstr_unpriv = "invalid read from stack off -4+0 size 4", + /* in privileged mode reads from uninitialized stack locations are permitted */ + .result = ACCEPT, }, { "Spill a u32 const scalar. Refill as u16. Offset to skb->data", diff --git a/tools/testing/selftests/bpf/verifier/var_off.c b/tools/testing/selftests/bpf/verifier/var_off.c index d37f512fad16..b183e26c03f1 100644 --- a/tools/testing/selftests/bpf/verifier/var_off.c +++ b/tools/testing/selftests/bpf/verifier/var_off.c @@ -212,31 +212,6 @@ .result = REJECT, .prog_type = BPF_PROG_TYPE_LWT_IN, }, -{ - "indirect variable-offset stack access, max_off+size > max_initialized", - .insns = { - /* Fill only the second from top 8 bytes of the stack. */ - BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0), - /* Get an unknown value. */ - BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0), - /* Make it small and 4-byte aligned. */ - BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4), - BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16), - /* Add it to fp. We now have either fp-12 or fp-16, but we don't know - * which. fp-12 size 8 is partially uninitialized stack. - */ - BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10), - /* Dereference it indirectly. */ - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .fixup_map_hash_8b = { 5 }, - .errstr = "invalid indirect read from stack R2 var_off", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_LWT_IN, -}, { "indirect variable-offset stack access, min_off < min_initialized", .insns = { @@ -289,33 +264,6 @@ .result = ACCEPT, .prog_type = BPF_PROG_TYPE_CGROUP_SKB, }, -{ - "indirect variable-offset stack access, uninitialized", - .insns = { - BPF_MOV64_IMM(BPF_REG_2, 6), - BPF_MOV64_IMM(BPF_REG_3, 28), - /* Fill the top 16 bytes of the stack. */ - BPF_ST_MEM(BPF_W, BPF_REG_10, -16, 0), - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - /* Get an unknown value. */ - BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1, 0), - /* Make it small and 4-byte aligned. */ - BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 4), - BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16), - /* Add it to fp. We now have either fp-12 or fp-16, we don't know - * which, but either way it points to initialized stack. - */ - BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_10), - BPF_MOV64_IMM(BPF_REG_5, 8), - /* Dereference it indirectly. */ - BPF_EMIT_CALL(BPF_FUNC_getsockopt), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - }, - .errstr = "invalid indirect read from stack R4 var_off", - .result = REJECT, - .prog_type = BPF_PROG_TYPE_SOCK_OPS, -}, { "indirect variable-offset stack access, ok", .insns = {
On Thu, Jul 11, 2024 at 09:43:21PM +0300, Maxim Mikityanskiy wrote:
From: Eduard Zingerman eddyz87@gmail.com
[ Upstream commit 6715df8d5d24655b9fd368e904028112b54c7de1 ]
This commits updates the following functions to allow reads from uninitialized stack locations when env->allow_uninit_stack option is enabled:
- check_stack_read_fixed_off()
- check_stack_range_initialized(), called from:
- check_stack_read_var_off()
- check_helper_mem_access()
Such change allows to relax logic in stacksafe() to treat STACK_MISC and STACK_INVALID in a same way and make the following stack slot configurations equivalent:
| Cached state | Current state | | stack slot | stack slot | |------------------+------------------| | STACK_INVALID or | STACK_INVALID or | | STACK_MISC | STACK_SPILL or | | | STACK_MISC or | | | STACK_ZERO or | | | STACK_DYNPTR |
This leads to significant verification speed gains (see below).
The idea was suggested by Andrii Nakryiko [1] and initial patch was created by Alexei Starovoitov [2].
Currently the env->allow_uninit_stack is allowed for programs loaded by users with CAP_PERFMON or CAP_SYS_ADMIN capabilities.
A number of test cases from verifier/*.c were expecting uninitialized stack access to be an error. These test cases were updated to execute in unprivileged mode (thus preserving the tests).
The test progs/test_global_func10.c expected "invalid indirect read from stack" error message because of the access to uninitialized memory region. This error is no longer possible in privileged mode. The test is updated to provoke an error "invalid indirect access to stack" because of access to invalid stack address (such error is not verified by progs/test_global_func*.c series of tests).
The following tests had to be removed because these can't be made unprivileged:
- verifier/sock.c:
stack_value" BPF_PROG_TYPE_SCHED_CLS programs are not executed in unprivileged mode.
- "sk_storage_get(map, skb->sk, &stack_value, 1): partially init
- verifier/var_off.c:
These tests verify that access to uninitialized stack values is detected when stack offset is not a constant. However, variable stack access is prohibited in unprivileged mode, thus these tests are no longer valid.
- "indirect variable-offset stack access, max_off+size > max_initialized"
- "indirect variable-offset stack access, uninitialized"
Here is veristat log comparing this patch with current master on a set of selftest binaries listed in tools/testing/selftests/bpf/veristat.cfg and cilium BPF binaries (see [3]):
$ ./veristat -e file,prog,states -C -f 'states_pct<-30' master.log current.log File Program States (A) States (B) States (DIFF)
bpf_host.o tail_handle_ipv6_from_host 349 244 -105 (-30.09%) bpf_host.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_lxc.o tail_handle_nat_fwd_ipv4 1320 895 -425 (-32.20%) bpf_sock.o cil_sock4_connect 70 48 -22 (-31.43%) bpf_sock.o cil_sock4_sendmsg 68 46 -22 (-32.35%) bpf_xdp.o tail_handle_nat_fwd_ipv4 1554 803 -751 (-48.33%) bpf_xdp.o tail_lb_ipv4 6457 2473 -3984 (-61.70%) bpf_xdp.o tail_lb_ipv6 7249 3908 -3341 (-46.09%) pyperf600_bpf_loop.bpf.o on_event 287 145 -142 (-49.48%) strobemeta.bpf.o on_event 15915 4772 -11143 (-70.02%) strobemeta_nounroll2.bpf.o on_event 17087 3820 -13267 (-77.64%) xdp_synproxy_kern.bpf.o syncookie_tc 21271 6635 -14636 (-68.81%) xdp_synproxy_kern.bpf.o syncookie_xdp 23122 6024 -17098 (-73.95%)
Note: I limited selection by states_pct<-30%.
Inspection of differences in pyperf600_bpf_loop behavior shows that the following patch for the test removes almost all differences:
- a/tools/testing/selftests/bpf/progs/pyperf.h + b/tools/testing/selftests/bpf/progs/pyperf.h @ -266,8 +266,8 @ int __on_event(struct bpf_raw_tracepoint_args *ctx) } if (event->pthread_match || !pidData->use_tls) { - void* frame_ptr; - FrameData frame; + void* frame_ptr = 0; + FrameData frame = {}; Symbol sym = {}; int cur_cpu = bpf_get_smp_processor_id();W/o this patch the difference comes from the following pattern (for different variables):
static bool get_frame_data(... FrameData *frame ...) { ... bpf_probe_read_user(&frame->f_code, ...); if (!frame->f_code) return false; ... bpf_probe_read_user(&frame->co_name, ...); if (frame->co_name) ...; } int __on_event(struct bpf_raw_tracepoint_args *ctx) { FrameData frame; ... get_frame_data(... &frame ...) // indirectly via a bpf_loop & callback ... } SEC("raw_tracepoint/kfree_skb") int on_event(struct bpf_raw_tracepoint_args* ctx) { ... ret |= __on_event(ctx); ret |= __on_event(ctx); ... }With regards to value `frame->co_name` the following is important:
Because of the conditional `if (!frame->f_code)` each call to __on_event() produces two states, one with `frame->co_name` marked as STACK_MISC, another with it as is (and marked STACK_INVALID on a first call).
The call to bpf_probe_read_user() does not mark stack slots corresponding to `&frame->co_name` as REG_LIVE_WRITTEN but it marks these slots as BPF_MISC, this happens because of the following loop in the check_helper_call():
for (i = 0; i < meta.access_size; i++) { err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1, false); if (err) return err; }
Note the size of the write, it is a one byte write for each byte touched by a helper. The BPF_B write does not lead to write marks for the target stack slot.
Which means that w/o this patch when second __on_event() call is verified `if (frame->co_name)` will propagate read marks first to a stack slot with STACK_MISC marks and second to a stack slot with STACK_INVALID marks and these states would be considered different.
[1] https://lore.kernel.org/bpf/CAEf4BzY3e+ZuC6HUa8dCiUovQRg2SzEk7M-dSkqNZyn=xEm... [2] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu... [3] git@github.com:anakryiko/cilium.git
Suggested-by: Andrii Nakryiko andrii@kernel.org Co-developed-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Eduard Zingerman eddyz87@gmail.com Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20230219200427.606541-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Maxim Mikityanskiy maxim@isovalent.com
Backporting to address the complexity regression introduced by commit 71f656a50176 ("bpf: Fix to preserve reg parent/live fields when copying range info"), that affects Cilium built with LLVM 18.
All now queued up, thanks.
greg k-h
linux-stable-mirror@lists.linaro.org
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Greg KH -
Greg Kroah-Hartman
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Maxim Mikityanskiy -
Sherry Yang -
Shung-Hsi Yu