Subject: Re: [syzbot] WARNING in bpf_verifier_vlog

From: [email-masked]
Date: Fri, 9 Sep 2022 14:43:18 -0700

On 09/09, Peilin Ye wrote:
> Hi all,

> On Fri, Sep 09, 2022 at 12:54:06PM -0700, [email-masked] wrote:
> > On 09/09, Benjamin Tissoires wrote:
> > Yeah, good point. I've run the repro. I think the issue is that
> > syzkaller is able to pass btf with a super long random name which
> > then hits BPF_VERIFIER_TMP_LOG_SIZE while printing the verifier
> > log line. Seems like a non-issue to me, but maybe we need to
> > add some extra validation..

> In btf_func_proto_check_meta():

> 	if (t->name_off) {
> 		btf_verifier_log_type(env, t, "Invalid name");
> 		return -EINVAL;
> 	}

> In the verifier log, maybe we should just say that  
> BTF_KIND_FUNC_PROTO "must
> not have a name" [1], instead of printing out the user-provided
> (potentially very long) name and say it's "Invalid" ?

> Similarly, for name-too-long errors, should we truncate the name to
> KSYM_NAME_LEN bytes (see __btf_name_valid()) in the log ?

Both suggestions sound good to me. Care to cook and send a patch with a
fix?

> [1] commit 2667a2626f4d ("bpf: btf: Add BTF_KIND_FUNC and  
> BTF_KIND_FUNC_PROTO")

> Thanks,
> Peilin Ye