netdev - Re: [PATCH bpf] bpf, test_run: Fix use-after-free issue in eth_skb_pkt

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Message-ID: <CAG_fn=VqUi=sGzz+0PJ9L7QrtOcgcn0ju=30BEGwB=D728wE8A@mail.gmail.com>
Date: Mon, 2 Dec 2024 10:32:04 +0100
From: Alexander Potapenko <glider@...gle.com>
To: Shigeru Yoshida <syoshida@...hat.com>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org, 
	yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org, 
	sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, 
	hawk@...nel.org, lorenzo@...nel.org, toke@...hat.com, bpf@...r.kernel.org, 
	netdev@...r.kernel.org, syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH bpf] bpf, test_run: Fix use-after-free issue in eth_skb_pkt_type()

On Sun, Dec 1, 2024 at 4:27 PM Shigeru Yoshida <syoshida@...hat.com> wrote:
>
> KMSAN reported a use-after-free issue in eth_skb_pkt_type()[1]. The
> cause of the issue was that eth_skb_pkt_type() accessed skb's data
> that didn't contain an Ethernet header. This occurs when
> bpf_prog_test_run_xdp() passes an invalid value as the user_data
> argument to bpf_test_init().

Hi Shigeru,

Thanks for taking care of this!

Am I understanding right that this bug was reported by your own
syzkaller instance?

Otherwise, if the report originates from syzkaller.appspot.com, could
you please append the bug hash to the Reported-by: tag?