linux-kernel - Re: [PATCH] bpf: Ensure BPF programs testing skb context initialization

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Message-ID: <bf687c6d-50ae-4252-9861-3e58f82f42f9@linux.dev>
Date: Wed, 17 Jul 2024 12:16:16 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, revest@...gle.com,
 syzbot+cca39e6e84a367a7e6f6@...kaller.appspotmail.com,
 alexei.starovoitov@...il.com, Michal Switala <michal.switala@...ogain.com>
Subject: Re: [PATCH] bpf: Ensure BPF programs testing skb context
 initialization

On 7/17/24 6:28 AM, Toke Høiland-Jørgensen wrote:
>> It looks very similar to
>> https://lore.kernel.org/bpf/000000000000f6531b061494e696@google.com/. It has
>> been fixed in commit 5bcf0dcbf906 ("xdp: use flags field to disambiguate
>> broadcast redirect")
>>
>> I tried the C repro. I can reproduce in the bpf tree also which should have the
>> fix. I cannot reproduce in the bpf-next though.
>>
>> Cc Toke who knows more details here.
> 
> Hmm, yeah, it does look kinda similar. Do you mean that the C repro from
> this new report triggers the crash for you on the current -bpf tree?

I was able to repro in bpf tree ~two days ago but not now. The bpf tree has been 
fast forwarded and has the 6.10 changes. I just tried linux-stable/linux-6.9.y 
which has the fix in the commit 5bcf0dcbf906. The syzbot report (against the 
36534d3c5453) also has that fix.

In particular, the syzbot repro I tried:
https://syzkaller.appspot.com/text?tag=ReproC&x=17caa30a980000