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+d2a2c639d03ac200a...@syzkaller.appspotmail.com Closes: https://lore.kernel.org/bpf/0000000000000f823606139fa...@google.com/ Fixes: 011832b97b311 ("bpf: Introduce may_goto instruction") Signed-off-by: Jiayuan Chen <mr...@163.com> --- kernel/bpf/core.c | 19 +++++++++++++++---- kernel/bpf/verifier.c | 7 +++++++ 2 files changed, 22 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index da729cbbaeb9..a0200fbbace9 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2290,17 +2290,18 @@ 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 +2381,18 @@ 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]; + /* may_goto may cause stack size > 512, leading to idx out-of-bounds. + * But for non-JITed programs, we don't need bpf_func, so no bounds + * check needed. + */ + if (!fp->jit_requested && + !WARN_ON_ONCE(idx >= ARRAY_SIZE(interpreters))) { + 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
