On Thu, Feb 13, 2025 at 5:13 AM Jiayuan Chen mrpre@163.com wrote:
may_goto uses an additional 8 bytes on the stack, which causes the interpreters[] array to go out of bounds when calculating index by stack_size.
- If a BPF program is rewritten, re-evaluate the stack size. For non-JIT
cases, reject loading directly.
- For non-JIT cases, calculating interpreters[idx] may still cause
out-of-bounds array access, and just warn about it.
- For jit_requested cases, the execution of bpf_func also needs to be
warned. So Move the definition of function __bpf_prog_ret0_warn out of the macro definition CONFIG_BPF_JIT_ALWAYS_ON
Reported-by: syzbot+d2a2c639d03ac200a4f1@syzkaller.appspotmail.com Closes: https://lore.kernel.org/bpf/0000000000000f823606139faa5d@google.com/ Fixes: 011832b97b311 ("bpf: Introduce may_goto instruction") Signed-off-by: Jiayuan Chen mrpre@163.com
kernel/bpf/core.c | 18 ++++++++++++++---- kernel/bpf/verifier.c | 7 +++++++ 2 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index da729cbbaeb9..59291261f825 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2269,6 +2269,9 @@ EVAL6(PROG_NAME_LIST, 32, 64, 96, 128, 160, 192) EVAL6(PROG_NAME_LIST, 224, 256, 288, 320, 352, 384) EVAL4(PROG_NAME_LIST, 416, 448, 480, 512) };
+#define MAX_INTERPRETERS_CALLBACK (sizeof(interpreters) / sizeof(*interpreters))
There is ARRAY_SIZE macro.
#undef PROG_NAME_LIST #define PROG_NAME_LIST(stack_size) PROG_NAME_ARGS(stack_size), static __maybe_unused @@ -2290,17 +2293,18 @@ void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth) insn->code = BPF_JMP | BPF_CALL_ARGS; } #endif -#else +#endif
static unsigned int __bpf_prog_ret0_warn(const void *ctx, const struct bpf_insn *insn) { /* If this handler ever gets executed, then BPF_JIT_ALWAYS_ON
* is not working properly, so warn about it!
* is not working properly, or interpreter is being used when* prog->jit_requested is not 0, so warn about it! */ WARN_ON_ONCE(1); return 0;} -#endif
bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog *fp) @@ -2380,8 +2384,14 @@ static void bpf_prog_select_func(struct bpf_prog *fp) { #ifndef CONFIG_BPF_JIT_ALWAYS_ON u32 stack_depth = max_t(u32, fp->aux->stack_depth, 1);
u32 idx = (round_up(stack_depth, 32) / 32) - 1;
fp->bpf_func = interpreters[(round_up(stack_depth, 32) / 32) - 1];
if (!fp->jit_requested) {
I don't think above check is necessary. Why not just if (WARN_ON_ONCE(idx >= ARRAY_SIZE(interpreters))) fp->bpf_func = __bpf_prog_ret0_warn; else fp->bpf_func = interpreters[idx];
WARN_ON_ONCE(idx >= MAX_INTERPRETERS_CALLBACK);fp->bpf_func = interpreters[idx];} else {fp->bpf_func = __bpf_prog_ret0_warn;}#else fp->bpf_func = __bpf_prog_ret0_warn; #endif diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9971c03adfd5..fcd302904ba0 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21882,6 +21882,13 @@ static int do_misc_fixups(struct bpf_verifier_env *env) if (subprogs[cur_subprog + 1].start == i + delta + 1) { subprogs[cur_subprog].stack_depth += stack_depth_extra; subprogs[cur_subprog].stack_extra = stack_depth_extra;
stack_depth = subprogs[cur_subprog].stack_depth;if (stack_depth > MAX_BPF_STACK && !prog->jit_requested) {verbose(env, "stack size %d(extra %d) is too large\n",stack_depth, stack_depth_extra);return -EINVAL;} cur_subprog++; stack_depth = subprogs[cur_subprog].stack_depth; stack_depth_extra = 0;-- 2.47.1