On Thu, Feb 13, 2025 at 5:13 AM Jiayuan Chen <mrpre@xxxxxxx> 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. > > 1. If a BPF program is rewritten, re-evaluate the stack size. For non-JIT > cases, reject loading directly. > > 2. For non-JIT cases, calculating interpreters[idx] may still cause > out-of-bounds array access, and just warn about it. > > 3. 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@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/bpf/0000000000000f823606139faa5d@xxxxxxxxxx/ > Fixes: 011832b97b311 ("bpf: Introduce may_goto instruction") > Signed-off-by: Jiayuan Chen <mrpre@xxxxxxx> > --- > 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 >
