From: Eduard Zingerman eddyz87@gmail.com

commit 27e88bc4df1d80888fe1aaca786a7cc6e69587e2 upstream.

Add a utility function, looking for a subprogram containing a given instruction index, rewrite find_subprog() to use this function.

Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- kernel/bpf/verifier.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d6a4102312fa..7322ac0c69ed 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2636,16 +2636,36 @@ static int cmp_subprogs(const void *a, const void *b) ((struct bpf_subprog_info *)b)->start; }

+/* Find subprogram that contains instruction at 'off' */ +static struct bpf_subprog_info *find_containing_subprog(struct bpf_verifier_env *env, int off) +{ + struct bpf_subprog_info *vals = env->subprog_info; + int l, r, m; + + if (off >= env->prog->len || off < 0 || env->subprog_cnt == 0) + return NULL; + + l = 0; + r = env->subprog_cnt - 1; + while (l < r) { + m = l + (r - l + 1) / 2; + if (vals[m].start <= off) + l = m; + else + r = m - 1; + } + return &vals[l]; +} + +/* Find subprogram that starts exactly at 'off' */ static int find_subprog(struct bpf_verifier_env *env, int off) { struct bpf_subprog_info *p;

- p = bsearch(&off, env->subprog_info, env->subprog_cnt, - sizeof(env->subprog_info[0]), cmp_subprogs); - if (!p) + p = find_containing_subprog(env, off); + if (!p || p->start != off) return -ENOENT; return p - env->subprog_info; - }

static int add_subprog(struct bpf_verifier_env *env, int off)

From: Eduard Zingerman eddyz87@gmail.com

commit b238e187b4a2d3b54d80aec05a9cab6466b79dde upstream.

Use BPF helper number instead of function pointer in bpf_helper_changes_pkt_data(). This would simplify usage of this function in verifier.c:check_cfg() (in a follow-up patch), where only helper number is easily available and there is no real need to lookup helper proto.

Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-3-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- include/linux/filter.h | 2 +- kernel/bpf/core.c | 2 +- kernel/bpf/verifier.c | 2 +- net/core/filter.c | 61 +++++++++++++++++++----------------------- 4 files changed, 30 insertions(+), 37 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h index 5090e940ba3e..adf65eacade0 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -915,7 +915,7 @@ bool bpf_jit_needs_zext(void); bool bpf_jit_supports_subprog_tailcalls(void); bool bpf_jit_supports_kfunc_call(void); bool bpf_jit_supports_far_kfunc_call(void); -bool bpf_helper_changes_pkt_data(void *func); +bool bpf_helper_changes_pkt_data(enum bpf_func_id func_id);

static inline bool bpf_dump_raw_ok(const struct cred *cred) { diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 02f327f05fd6..81fd1bb99416 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2893,7 +2893,7 @@ void __weak bpf_jit_compile(struct bpf_prog *prog) { }

-bool __weak bpf_helper_changes_pkt_data(void *func) +bool __weak bpf_helper_changes_pkt_data(enum bpf_func_id func_id) { return false; } diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7322ac0c69ed..329b66516a85 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10007,7 +10007,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn }

/* With LD_ABS/IND some JITs save/restore skb from r1. */ - changes_data = bpf_helper_changes_pkt_data(fn->func); + changes_data = bpf_helper_changes_pkt_data(func_id); if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) { verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n", func_id_name(func_id), func_id); diff --git a/net/core/filter.c b/net/core/filter.c index 84992279f4b1..c44754ff4abe 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7860,42 +7860,35 @@ static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_ipv6_proto = {

#endif /* CONFIG_INET */

-bool bpf_helper_changes_pkt_data(void *func) +bool bpf_helper_changes_pkt_data(enum bpf_func_id func_id) { - if (func == bpf_skb_vlan_push || - func == bpf_skb_vlan_pop || - func == bpf_skb_store_bytes || - func == bpf_skb_change_proto || - func == bpf_skb_change_head || - func == sk_skb_change_head || - func == bpf_skb_change_tail || - func == sk_skb_change_tail || - func == bpf_skb_adjust_room || - func == sk_skb_adjust_room || - func == bpf_skb_pull_data || - func == sk_skb_pull_data || - func == bpf_clone_redirect || - func == bpf_l3_csum_replace || - func == bpf_l4_csum_replace || - func == bpf_xdp_adjust_head || - func == bpf_xdp_adjust_meta || - func == bpf_msg_pull_data || - func == bpf_msg_push_data || - func == bpf_msg_pop_data || - func == bpf_xdp_adjust_tail || -#if IS_ENABLED(CONFIG_IPV6_SEG6_BPF) - func == bpf_lwt_seg6_store_bytes || - func == bpf_lwt_seg6_adjust_srh || - func == bpf_lwt_seg6_action || -#endif -#ifdef CONFIG_INET - func == bpf_sock_ops_store_hdr_opt || -#endif - func == bpf_lwt_in_push_encap || - func == bpf_lwt_xmit_push_encap) + switch (func_id) { + case BPF_FUNC_clone_redirect: + case BPF_FUNC_l3_csum_replace: + case BPF_FUNC_l4_csum_replace: + case BPF_FUNC_lwt_push_encap: + case BPF_FUNC_lwt_seg6_action: + case BPF_FUNC_lwt_seg6_adjust_srh: + case BPF_FUNC_lwt_seg6_store_bytes: + case BPF_FUNC_msg_pop_data: + case BPF_FUNC_msg_pull_data: + case BPF_FUNC_msg_push_data: + case BPF_FUNC_skb_adjust_room: + case BPF_FUNC_skb_change_head: + case BPF_FUNC_skb_change_proto: + case BPF_FUNC_skb_change_tail: + case BPF_FUNC_skb_pull_data: + case BPF_FUNC_skb_store_bytes: + case BPF_FUNC_skb_vlan_pop: + case BPF_FUNC_skb_vlan_push: + case BPF_FUNC_store_hdr_opt: + case BPF_FUNC_xdp_adjust_head: + case BPF_FUNC_xdp_adjust_meta: + case BPF_FUNC_xdp_adjust_tail: return true; - - return false; + default: + return false; + } }

const struct bpf_func_proto bpf_event_output_data_proto __weak;

From: Eduard Zingerman eddyz87@gmail.com

commit 51081a3f25c742da5a659d7fc6fd77ebfdd555be upstream.

When processing calls to certain helpers, verifier invalidates all packet pointers in a current state. For example, consider the following program:

__attribute__((__noinline__)) long skb_pull_data(struct __sk_buff *sk, __u32 len) { return bpf_skb_pull_data(sk, len); }

SEC("tc") int test_invalidate_checks(struct __sk_buff *sk) { int *p = (void *)(long)sk->data; if ((void *)(p + 1) > (void *)(long)sk->data_end) return TCX_DROP; skb_pull_data(sk, 0); *p = 42; return TCX_PASS; }

After a call to bpf_skb_pull_data() the pointer 'p' can't be used safely. See function filter.c:bpf_helper_changes_pkt_data() for a list of such helpers.

At the moment verifier invalidates packet pointers when processing helper function calls, and does not traverse global sub-programs when processing calls to global sub-programs. This means that calls to helpers done from global sub-programs do not invalidate pointers in the caller state. E.g. the program above is unsafe, but is not rejected by verifier.

This commit fixes the omission by computing field bpf_subprog_info->changes_pkt_data for each sub-program before main verification pass. changes_pkt_data should be set if: - subprogram calls helper for which bpf_helper_changes_pkt_data returns true; - subprogram calls a global function, for which bpf_subprog_info->changes_pkt_data should be set.

The verifier.c:check_cfg() pass is modified to compute this information. The commit relies on depth first instruction traversal done by check_cfg() and absence of recursive function calls: - check_cfg() would eventually visit every call to subprogram S in a state when S is fully explored; - when S is fully explored: - every direct helper call within S is explored (and thus changes_pkt_data is set if needed); - every call to subprogram S1 called by S was visited with S1 fully explored (and thus S inherits changes_pkt_data from S1).

The downside of such approach is that dead code elimination is not taken into account: if a helper call inside global function is dead because of current configuration, verifier would conservatively assume that the call occurs for the purpose of the changes_pkt_data computation.

Reported-by: Nick Zavaritsky mejedi@gmail.com Closes: https://lore.kernel.org/bpf/0498CA22-5779-4767-9C0C-A9515CEA711F@gmail.com/ Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-4-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org [shung-hsi.yu: do not use bitfield in "struct bpf_subprog_info" because commit 406a6fa44bfb ("bpf: use bitfields for simple per-subprog bool flags") is not present and minor context difference in check_func_call() because commit 491dd8edecbc ("bpf: Emit global subprog name in verifier logs") is not present. ] Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 32 +++++++++++++++++++++++++++++++- 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 92919d52f7e1..32e89758176b 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -573,6 +573,7 @@ struct bpf_subprog_info { bool tail_call_reachable; bool has_ld_abs; bool is_async_cb; + bool changes_pkt_data; };

struct bpf_verifier_env; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 329b66516a85..154513999e03 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9364,6 +9364,8 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,

if (env->log.level & BPF_LOG_LEVEL) verbose(env, "Func#%d is global and valid. Skipping.\n", subprog); + if (env->subprog_info[subprog].changes_pkt_data) + clear_all_pkt_pointers(env); clear_caller_saved_regs(env, caller->regs);

/* All global functions return a 64-bit SCALAR_VALUE */ @@ -15114,6 +15116,29 @@ static int check_return_code(struct bpf_verifier_env *env) return 0; }

+static void mark_subprog_changes_pkt_data(struct bpf_verifier_env *env, int off) +{ + struct bpf_subprog_info *subprog; + + subprog = find_containing_subprog(env, off); + subprog->changes_pkt_data = true; +} + +/* 't' is an index of a call-site. + * 'w' is a callee entry point. + * Eventually this function would be called when env->cfg.insn_state[w] == EXPLORED. + * Rely on DFS traversal order and absence of recursive calls to guarantee that + * callee's change_pkt_data marks would be correct at that moment. + */ +static void merge_callee_effects(struct bpf_verifier_env *env, int t, int w) +{ + struct bpf_subprog_info *caller, *callee; + + caller = find_containing_subprog(env, t); + callee = find_containing_subprog(env, w); + caller->changes_pkt_data |= callee->changes_pkt_data; +} + /* non-recursive DFS pseudo code * 1 procedure DFS-iterative(G,v): * 2 label v as discovered @@ -15247,6 +15272,7 @@ static int visit_func_call_insn(int t, struct bpf_insn *insns, bool visit_callee) { int ret, insn_sz; + int w;

insn_sz = bpf_is_ldimm64(&insns[t]) ? 2 : 1; ret = push_insn(t, t + insn_sz, FALLTHROUGH, env); @@ -15258,8 +15284,10 @@ static int visit_func_call_insn(int t, struct bpf_insn *insns, mark_jmp_point(env, t + insn_sz);

if (visit_callee) { + w = t + insns[t].imm + 1; mark_prune_point(env, t); - ret = push_insn(t, t + insns[t].imm + 1, BRANCH, env); + merge_callee_effects(env, t, w); + ret = push_insn(t, w, BRANCH, env); } return ret; } @@ -15311,6 +15339,8 @@ static int visit_insn(int t, struct bpf_verifier_env *env) mark_prune_point(env, t); mark_jmp_point(env, t); } + if (bpf_helper_call(insn) && bpf_helper_changes_pkt_data(insn->imm)) + mark_subprog_changes_pkt_data(env, t); if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) { struct bpf_kfunc_call_arg_meta meta;

From: Eduard Zingerman eddyz87@gmail.com

commit 3f23ee5590d9605dbde9a5e1d4b97637a4803329 upstream.

Check if verifier is aware of packet pointers invalidation done in global functions. Based on a test shared by Nick Zavaritsky in [0].

[0] https://lore.kernel.org/bpf/0498CA22-5779-4767-9C0C-A9515CEA711F@gmail.com/

Suggested-by: Nick Zavaritsky mejedi@gmail.com Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-5-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- .../selftests/bpf/progs/verifier_sock.c | 28 +++++++++++++++++++ 1 file changed, 28 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_sock.c b/tools/testing/selftests/bpf/progs/verifier_sock.c index ee76b51005ab..e85f0f1deac7 100644 --- a/tools/testing/selftests/bpf/progs/verifier_sock.c +++ b/tools/testing/selftests/bpf/progs/verifier_sock.c @@ -977,4 +977,32 @@ l1_%=: r0 = *(u8*)(r7 + 0); \ : __clobber_all); }

+__noinline +long skb_pull_data2(struct __sk_buff *sk, __u32 len) +{ + return bpf_skb_pull_data(sk, len); +} + +__noinline +long skb_pull_data1(struct __sk_buff *sk, __u32 len) +{ + return skb_pull_data2(sk, len); +} + +/* global function calls bpf_skb_pull_data(), which invalidates packet + * pointers established before global function call. + */ +SEC("tc") +__failure __msg("invalid mem access") +int invalidate_pkt_pointers_from_global_func(struct __sk_buff *sk) +{ + int *p = (void *)(long)sk->data; + + if ((void *)(p + 1) > (void *)(long)sk->data_end) + return TCX_DROP; + skb_pull_data1(sk, 0); + *p = 42; /* this is unsafe */ + return TCX_PASS; +} + char _license[] SEC("license") = "GPL";

From: Eduard Zingerman eddyz87@gmail.com

commit 81f6d0530ba031b5f038a091619bf2ff29568852 upstream.

When processing calls to global sub-programs, verifier decides whether to invalidate all packet pointers in current state depending on the changes_pkt_data property of the global sub-program.

Because of this, an extension program replacing a global sub-program must be compatible with changes_pkt_data property of the sub-program being replaced.

This commit: - adds changes_pkt_data flag to struct bpf_prog_aux: - this flag is set in check_cfg() for main sub-program; - in jit_subprogs() for other sub-programs; - modifies bpf_check_attach_btf_id() to check changes_pkt_data flag; - moves call to check_attach_btf_id() after the call to check_cfg(), because it needs changes_pkt_data flag to be set:

bpf_check: ... ... - check_attach_btf_id resolve_pseudo_ldimm64 resolve_pseudo_ldimm64 --> bpf_prog_is_offloaded bpf_prog_is_offloaded check_cfg check_cfg + check_attach_btf_id ... ...

The following fields are set by check_attach_btf_id(): - env->ops - prog->aux->attach_btf_trace - prog->aux->attach_func_name - prog->aux->attach_func_proto - prog->aux->dst_trampoline - prog->aux->mod - prog->aux->saved_dst_attach_type - prog->aux->saved_dst_prog_type - prog->expected_attach_type

Neither of these fields are used by resolve_pseudo_ldimm64() or bpf_prog_offload_verifier_prep() (for netronome and netdevsim drivers), so the reordering is safe.

Suggested-by: Alexei Starovoitov alexei.starovoitov@gmail.com Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-6-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org [ shung-hsi.yu: adapt to missing fields in "struct bpf_prog_aux". Context difference in jit_subprogs() because BPF Exception is not supported. Context difference in bpf_check() because commit 5b5f51bff1b6 "bpf: no_caller_saved_registers attribute for helper calls" is not present. ] Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- include/linux/bpf.h | 1 + kernel/bpf/verifier.c | 16 ++++++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 035e627f94f6..17de12a98f85 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1430,6 +1430,7 @@ struct bpf_prog_aux { bool sleepable; bool tail_call_reachable; bool xdp_has_frags; + bool changes_pkt_data; /* BTF_KIND_FUNC_PROTO for valid attach_btf_id */ const struct btf_type *attach_func_proto; /* function name for valid attach_btf_id */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 154513999e03..d9cf75b765f0 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15462,6 +15462,7 @@ static int check_cfg(struct bpf_verifier_env *env) } } ret = 0; /* cfg looks good */ + env->prog->aux->changes_pkt_data = env->subprog_info[0].changes_pkt_data;

err_free: kvfree(insn_state); @@ -18622,6 +18623,7 @@ static int jit_subprogs(struct bpf_verifier_env *env) } func[i]->aux->num_exentries = num_exentries; func[i]->aux->tail_call_reachable = env->subprog_info[i].tail_call_reachable; + func[i]->aux->changes_pkt_data = env->subprog_info[i].changes_pkt_data; func[i] = bpf_int_jit_compile(func[i]); if (!func[i]->jited) { err = -ENOTSUPP; @@ -19934,6 +19936,12 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, "Extension programs should be JITed\n"); return -EINVAL; } + if (prog->aux->changes_pkt_data && + !aux->func[subprog]->aux->changes_pkt_data) { + bpf_log(log, + "Extension program changes packet data, while original does not\n"); + return -EINVAL; + } } if (!tgt_prog->jited) { bpf_log(log, "Can attach to only JITed progs\n"); @@ -20361,10 +20369,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3 if (ret < 0) goto skip_full_check;

- ret = check_attach_btf_id(env); - if (ret) - goto skip_full_check; - ret = resolve_pseudo_ldimm64(env); if (ret < 0) goto skip_full_check; @@ -20379,6 +20383,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3 if (ret < 0) goto skip_full_check;

+ ret = check_attach_btf_id(env); + if (ret) + goto skip_full_check; + ret = do_check_subprogs(env); ret = ret ?: do_check_main(env);

From: Eduard Zingerman eddyz87@gmail.com

commit 89ff40890d8f12a7d7e93fb602cc27562f3834f0 upstream.

Try different combinations of global functions replacement: - replace function that changes packet data with one that doesn't; - replace function that changes packet data with one that does; - replace function that doesn't change packet data with one that does; - replace function that doesn't change packet data with one that doesn't;

Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-7-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- .../bpf/prog_tests/changes_pkt_data.c | 76 +++++++++++++++++++ .../selftests/bpf/progs/changes_pkt_data.c | 26 +++++++ .../bpf/progs/changes_pkt_data_freplace.c | 18 +++++ 3 files changed, 120 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c create mode 100644 tools/testing/selftests/bpf/progs/changes_pkt_data.c create mode 100644 tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c

diff --git a/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c b/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c new file mode 100644 index 000000000000..c0c7202f6c5c --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c @@ -0,0 +1,76 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "bpf/libbpf.h" +#include "changes_pkt_data_freplace.skel.h" +#include "changes_pkt_data.skel.h" +#include <test_progs.h> + +static void print_verifier_log(const char *log) +{ + if (env.verbosity >= VERBOSE_VERY) + fprintf(stdout, "VERIFIER LOG:\n=============\n%s=============\n", log); +} + +static void test_aux(const char *main_prog_name, const char *freplace_prog_name, bool expect_load) +{ + struct changes_pkt_data_freplace *freplace = NULL; + struct bpf_program *freplace_prog = NULL; + LIBBPF_OPTS(bpf_object_open_opts, opts); + struct changes_pkt_data *main = NULL; + char log[16*1024]; + int err; + + opts.kernel_log_buf = log; + opts.kernel_log_size = sizeof(log); + if (env.verbosity >= VERBOSE_SUPER) + opts.kernel_log_level = 1 | 2 | 4; + main = changes_pkt_data__open_opts(&opts); + if (!ASSERT_OK_PTR(main, "changes_pkt_data__open")) + goto out; + err = changes_pkt_data__load(main); + print_verifier_log(log); + if (!ASSERT_OK(err, "changes_pkt_data__load")) + goto out; + freplace = changes_pkt_data_freplace__open_opts(&opts); + if (!ASSERT_OK_PTR(freplace, "changes_pkt_data_freplace__open")) + goto out; + freplace_prog = bpf_object__find_program_by_name(freplace->obj, freplace_prog_name); + if (!ASSERT_OK_PTR(freplace_prog, "freplace_prog")) + goto out; + bpf_program__set_autoload(freplace_prog, true); + bpf_program__set_autoattach(freplace_prog, true); + bpf_program__set_attach_target(freplace_prog, + bpf_program__fd(main->progs.dummy), + main_prog_name); + err = changes_pkt_data_freplace__load(freplace); + print_verifier_log(log); + if (expect_load) { + ASSERT_OK(err, "changes_pkt_data_freplace__load"); + } else { + ASSERT_ERR(err, "changes_pkt_data_freplace__load"); + ASSERT_HAS_SUBSTR(log, "Extension program changes packet data", "error log"); + } + +out: + changes_pkt_data_freplace__destroy(freplace); + changes_pkt_data__destroy(main); +} + +/* There are two global subprograms in both changes_pkt_data.skel.h: + * - one changes packet data; + * - another does not. + * It is ok to freplace subprograms that change packet data with those + * that either do or do not. It is only ok to freplace subprograms + * that do not change packet data with those that do not as well. + * The below tests check outcomes for each combination of such freplace. + */ +void test_changes_pkt_data_freplace(void) +{ + if (test__start_subtest("changes_with_changes")) + test_aux("changes_pkt_data", "changes_pkt_data", true); + if (test__start_subtest("changes_with_doesnt_change")) + test_aux("changes_pkt_data", "does_not_change_pkt_data", true); + if (test__start_subtest("doesnt_change_with_changes")) + test_aux("does_not_change_pkt_data", "changes_pkt_data", false); + if (test__start_subtest("doesnt_change_with_doesnt_change")) + test_aux("does_not_change_pkt_data", "does_not_change_pkt_data", true); +} diff --git a/tools/testing/selftests/bpf/progs/changes_pkt_data.c b/tools/testing/selftests/bpf/progs/changes_pkt_data.c new file mode 100644 index 000000000000..f87da8e9d6b3 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/changes_pkt_data.c @@ -0,0 +1,26 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> + +__noinline +long changes_pkt_data(struct __sk_buff *sk, __u32 len) +{ + return bpf_skb_pull_data(sk, len); +} + +__noinline __weak +long does_not_change_pkt_data(struct __sk_buff *sk, __u32 len) +{ + return 0; +} + +SEC("tc") +int dummy(struct __sk_buff *sk) +{ + changes_pkt_data(sk, 0); + does_not_change_pkt_data(sk, 0); + return 0; +} + +char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c b/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c new file mode 100644 index 000000000000..0e525beb8603 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> + +SEC("?freplace") +long changes_pkt_data(struct __sk_buff *sk, __u32 len) +{ + return bpf_skb_pull_data(sk, len); +} + +SEC("?freplace") +long does_not_change_pkt_data(struct __sk_buff *sk, __u32 len) +{ + return 0; +} + +char _license[] SEC("license") = "GPL";

From: Eduard Zingerman eddyz87@gmail.com

commit 1a4607ffba35bf2a630aab299e34dd3f6e658d70 upstream.

Tail-called programs could execute any of the helpers that invalidate packet pointers. Hence, conservatively assume that each tail call invalidates packet pointers.

Making the change in bpf_helper_changes_pkt_data() automatically makes use of check_cfg() logic that computes 'changes_pkt_data' effect for global sub-programs, such that the following program could be rejected:

int tail_call(struct __sk_buff *sk) { bpf_tail_call_static(sk, &jmp_table, 0); return 0; }

SEC("tc") int not_safe(struct __sk_buff *sk) { int *p = (void *)(long)sk->data; ... make p valid ... tail_call(sk); *p = 42; /* this is unsafe */ ... }

The tc_bpf2bpf.c:subprog_tc() needs change: mark it as a function that can invalidate packet pointers. Otherwise, it can't be freplaced with tailcall_freplace.c:entry_freplace() that does a tail call.

Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-8-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org [ shung-hsi.yu: drop changes to tools/testing/selftests/bpf/progs/tc_bpf2bpf.c because it is not present. ] Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- net/core/filter.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c index c44754ff4abe..40fc6ed49dcd 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7885,6 +7885,8 @@ bool bpf_helper_changes_pkt_data(enum bpf_func_id func_id) case BPF_FUNC_xdp_adjust_head: case BPF_FUNC_xdp_adjust_meta: case BPF_FUNC_xdp_adjust_tail: + /* tail-called program could call any of the above */ + case BPF_FUNC_tail_call: return true; default: return false;

From: Eduard Zingerman eddyz87@gmail.com

commit d9706b56e13b7916461ca6b4b731e169ed44ed09 upstream.

Add a test case with a tail call done from a global sub-program. Such tails calls should be considered as invalidating packet pointers.

Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-9-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- .../selftests/bpf/progs/verifier_sock.c | 28 +++++++++++++++++++ 1 file changed, 28 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_sock.c b/tools/testing/selftests/bpf/progs/verifier_sock.c index e85f0f1deac7..3c8f6646e33d 100644 --- a/tools/testing/selftests/bpf/progs/verifier_sock.c +++ b/tools/testing/selftests/bpf/progs/verifier_sock.c @@ -50,6 +50,13 @@ struct { __uint(map_flags, BPF_F_NO_PREALLOC); } sk_storage_map SEC(".maps");

+struct { + __uint(type, BPF_MAP_TYPE_PROG_ARRAY); + __uint(max_entries, 1); + __uint(key_size, sizeof(__u32)); + __uint(value_size, sizeof(__u32)); +} jmp_table SEC(".maps"); + SEC("cgroup/skb") __description("skb->sk: no NULL check") __failure __msg("invalid mem access 'sock_common_or_null'") @@ -1005,4 +1012,25 @@ int invalidate_pkt_pointers_from_global_func(struct __sk_buff *sk) return TCX_PASS; }

+__noinline +int tail_call(struct __sk_buff *sk) +{ + bpf_tail_call_static(sk, &jmp_table, 0); + return 0; +} + +/* Tail calls invalidate packet pointers. */ +SEC("tc") +__failure __msg("invalid mem access") +int invalidate_pkt_pointers_by_tail_call(struct __sk_buff *sk) +{ + int *p = (void *)(long)sk->data; + + if ((void *)(p + 1) > (void *)(long)sk->data_end) + return TCX_DROP; + tail_call(sk); + *p = 42; /* this is unsafe */ + return TCX_PASS; +} + char _license[] SEC("license") = "GPL";

From: Eduard Zingerman eddyz87@gmail.com

commit ac6542ad92759cda383ad62b4e4cbfc28136abc1 upstream.

bpf_prog_aux->func field might be NULL if program does not have subprograms except for main sub-program. The fixed commit does bpf_prog_aux->func access unconditionally, which might lead to null pointer dereference.

The bug could be triggered by replacing the following BPF program:

SEC("tc") int main_changes(struct __sk_buff *sk) { bpf_skb_pull_data(sk, 0); return 0; }

With the following BPF program:

SEC("freplace") long changes_pkt_data(struct __sk_buff *sk) { return bpf_skb_pull_data(sk, 0); }

bpf_prog_aux instance itself represents the main sub-program, use this property to fix the bug.

Fixes: 81f6d0530ba0 ("bpf: check changes_pkt_data property for extension programs") Reported-by: kernel test robot lkp@intel.com Reported-by: Dan Carpenter dan.carpenter@linaro.org Closes: https://lore.kernel.org/r/202412111822.qGw6tOyB-lkp@intel.com/ Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241212070711.427443-1-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- kernel/bpf/verifier.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d9cf75b765f0..bf8696b96491 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -19908,6 +19908,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, } if (tgt_prog) { struct bpf_prog_aux *aux = tgt_prog->aux; + bool tgt_changes_pkt_data;

if (bpf_prog_is_dev_bound(prog->aux) && !bpf_prog_dev_bound_match(prog, tgt_prog)) { @@ -19936,8 +19937,10 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, "Extension programs should be JITed\n"); return -EINVAL; } - if (prog->aux->changes_pkt_data && - !aux->func[subprog]->aux->changes_pkt_data) { + tgt_changes_pkt_data = aux->func + ? aux->func[subprog]->aux->changes_pkt_data + : aux->changes_pkt_data; + if (prog->aux->changes_pkt_data && !tgt_changes_pkt_data) { bpf_log(log, "Extension program changes packet data, while original does not\n"); return -EINVAL;

From: Eduard Zingerman eddyz87@gmail.com

commit 04789af756a4a43e72986185f66f148e65b32fed upstream.

Extend changes_pkt_data tests with test cases freplacing the main program that does not have subprograms. Try four combinations when both main program and replacement do and do not change packet data.

Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241212070711.427443-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- .../bpf/prog_tests/changes_pkt_data.c | 55 +++++++++++++++---- .../selftests/bpf/progs/changes_pkt_data.c | 27 ++++++--- .../bpf/progs/changes_pkt_data_freplace.c | 6 +- 3 files changed, 66 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c b/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c index c0c7202f6c5c..7526de379081 100644 --- a/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c +++ b/tools/testing/selftests/bpf/prog_tests/changes_pkt_data.c @@ -10,10 +10,14 @@ static void print_verifier_log(const char *log) fprintf(stdout, "VERIFIER LOG:\n=============\n%s=============\n", log); }

-static void test_aux(const char *main_prog_name, const char *freplace_prog_name, bool expect_load) +static void test_aux(const char *main_prog_name, + const char *to_be_replaced, + const char *replacement, + bool expect_load) { struct changes_pkt_data_freplace *freplace = NULL; struct bpf_program *freplace_prog = NULL; + struct bpf_program *main_prog = NULL; LIBBPF_OPTS(bpf_object_open_opts, opts); struct changes_pkt_data *main = NULL; char log[16*1024]; @@ -26,6 +30,10 @@ static void test_aux(const char *main_prog_name, const char *freplace_prog_name, main = changes_pkt_data__open_opts(&opts); if (!ASSERT_OK_PTR(main, "changes_pkt_data__open")) goto out; + main_prog = bpf_object__find_program_by_name(main->obj, main_prog_name); + if (!ASSERT_OK_PTR(main_prog, "main_prog")) + goto out; + bpf_program__set_autoload(main_prog, true); err = changes_pkt_data__load(main); print_verifier_log(log); if (!ASSERT_OK(err, "changes_pkt_data__load")) @@ -33,14 +41,14 @@ static void test_aux(const char *main_prog_name, const char *freplace_prog_name, freplace = changes_pkt_data_freplace__open_opts(&opts); if (!ASSERT_OK_PTR(freplace, "changes_pkt_data_freplace__open")) goto out; - freplace_prog = bpf_object__find_program_by_name(freplace->obj, freplace_prog_name); + freplace_prog = bpf_object__find_program_by_name(freplace->obj, replacement); if (!ASSERT_OK_PTR(freplace_prog, "freplace_prog")) goto out; bpf_program__set_autoload(freplace_prog, true); bpf_program__set_autoattach(freplace_prog, true); bpf_program__set_attach_target(freplace_prog, - bpf_program__fd(main->progs.dummy), - main_prog_name); + bpf_program__fd(main_prog), + to_be_replaced); err = changes_pkt_data_freplace__load(freplace); print_verifier_log(log); if (expect_load) { @@ -62,15 +70,38 @@ static void test_aux(const char *main_prog_name, const char *freplace_prog_name, * that either do or do not. It is only ok to freplace subprograms * that do not change packet data with those that do not as well. * The below tests check outcomes for each combination of such freplace. + * Also test a case when main subprogram itself is replaced and is a single + * subprogram in a program. */ void test_changes_pkt_data_freplace(void) { - if (test__start_subtest("changes_with_changes")) - test_aux("changes_pkt_data", "changes_pkt_data", true); - if (test__start_subtest("changes_with_doesnt_change")) - test_aux("changes_pkt_data", "does_not_change_pkt_data", true); - if (test__start_subtest("doesnt_change_with_changes")) - test_aux("does_not_change_pkt_data", "changes_pkt_data", false); - if (test__start_subtest("doesnt_change_with_doesnt_change")) - test_aux("does_not_change_pkt_data", "does_not_change_pkt_data", true); + struct { + const char *main; + const char *to_be_replaced; + bool changes; + } mains[] = { + { "main_with_subprogs", "changes_pkt_data", true }, + { "main_with_subprogs", "does_not_change_pkt_data", false }, + { "main_changes", "main_changes", true }, + { "main_does_not_change", "main_does_not_change", false }, + }; + struct { + const char *func; + bool changes; + } replacements[] = { + { "changes_pkt_data", true }, + { "does_not_change_pkt_data", false } + }; + char buf[64]; + + for (int i = 0; i < ARRAY_SIZE(mains); ++i) { + for (int j = 0; j < ARRAY_SIZE(replacements); ++j) { + snprintf(buf, sizeof(buf), "%s_with_%s", + mains[i].to_be_replaced, replacements[j].func); + if (!test__start_subtest(buf)) + continue; + test_aux(mains[i].main, mains[i].to_be_replaced, replacements[j].func, + mains[i].changes || !replacements[j].changes); + } + } } diff --git a/tools/testing/selftests/bpf/progs/changes_pkt_data.c b/tools/testing/selftests/bpf/progs/changes_pkt_data.c index f87da8e9d6b3..43cada48b28a 100644 --- a/tools/testing/selftests/bpf/progs/changes_pkt_data.c +++ b/tools/testing/selftests/bpf/progs/changes_pkt_data.c @@ -4,22 +4,35 @@ #include <bpf/bpf_helpers.h>

__noinline -long changes_pkt_data(struct __sk_buff *sk, __u32 len) +long changes_pkt_data(struct __sk_buff *sk) { - return bpf_skb_pull_data(sk, len); + return bpf_skb_pull_data(sk, 0); }

__noinline __weak -long does_not_change_pkt_data(struct __sk_buff *sk, __u32 len) +long does_not_change_pkt_data(struct __sk_buff *sk) { return 0; }

-SEC("tc") -int dummy(struct __sk_buff *sk) +SEC("?tc") +int main_with_subprogs(struct __sk_buff *sk) +{ + changes_pkt_data(sk); + does_not_change_pkt_data(sk); + return 0; +} + +SEC("?tc") +int main_changes(struct __sk_buff *sk) +{ + bpf_skb_pull_data(sk, 0); + return 0; +} + +SEC("?tc") +int main_does_not_change(struct __sk_buff *sk) { - changes_pkt_data(sk, 0); - does_not_change_pkt_data(sk, 0); return 0; }

diff --git a/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c b/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c index 0e525beb8603..f9a622705f1b 100644 --- a/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c +++ b/tools/testing/selftests/bpf/progs/changes_pkt_data_freplace.c @@ -4,13 +4,13 @@ #include <bpf/bpf_helpers.h>

SEC("?freplace") -long changes_pkt_data(struct __sk_buff *sk, __u32 len) +long changes_pkt_data(struct __sk_buff *sk) { - return bpf_skb_pull_data(sk, len); + return bpf_skb_pull_data(sk, 0); }

SEC("?freplace") -long does_not_change_pkt_data(struct __sk_buff *sk, __u32 len) +long does_not_change_pkt_data(struct __sk_buff *sk) { return 0; }