From: Florent Revest Date: Thu, 22 Apr 2021 23:55:42 +0000 (+0200) Subject: bpf: Notify user if we ever hit a bpf_snprintf verifier bug X-Git-Tag: howlett/maple/20220722_2~3257^2~46^2~2^2~1 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8e8ee109b02c0e90021d63cd20dd0157c021f7a4;p=users%2Fjedix%2Flinux-maple.git bpf: Notify user if we ever hit a bpf_snprintf verifier bug 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. Reported-by: Alexei Starovoitov Signed-off-by: Florent Revest Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20210422235543.4007694-2-revest@chromium.org --- 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