Messages in this thread Patch in this message | | | From | Florent Revest <> | Subject | [PATCH bpf-next 1/2] bpf: Notify user if we ever hit a bpf_snprintf verifier bug | Date | Fri, 23 Apr 2021 01:55:42 +0200 |
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In check_bpf_snprintf_call(), a map_direct_value_addr() of the fmt map should never fail because it has already been checked by ARG_PTR_TO_CONST_STR. But if it ever fails, it's better to error out with an explicit debug message rather than silently fail.
Signed-off-by: Florent Revest <revest@chromium.org> Reported-by: Alexei Starovoitov <ast@kernel.org> --- kernel/bpf/verifier.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 58730872f7e5..59799a9b014a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5940,8 +5940,10 @@ static int check_bpf_snprintf_call(struct bpf_verifier_env *env, fmt_map_off = fmt_reg->off + fmt_reg->var_off.value; err = fmt_map->ops->map_direct_value_addr(fmt_map, &fmt_addr, fmt_map_off); - if (err) - return err; + if (err) { + verbose(env, "verifier bug\n"); + return -EFAULT; + } fmt = (char *)(long)fmt_addr + fmt_map_off; /* We are also guaranteed that fmt+fmt_map_off is NULL terminated, we -- 2.31.1.498.g6c1eba8ee3d-goog
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