linux-kernel - Re: [syzbot] [net?] general protection fault in put

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Message-ID: <c5f83a88-b881-4358-87ca-b3feb5405ae7@kernel.org>
Date: Wed, 18 Dec 2024 19:06:32 +0100
From: Matthieu Baerts <matttbe@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, dsahern@...nel.org, horms@...nel.org,
 kuba@...nel.org, linux-kernel@...r.kernel.org, martineau@...nel.org,
 netdev@...r.kernel.org, pabeni@...hat.com,
 syzbot <syzbot+38a095a81f30d82884c1@...kaller.appspotmail.com>,
 syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] general protection fault in put_page (4)

Hi Eric,

On 17/12/2024 18:06, Eric Dumazet wrote:
> On Tue, Dec 17, 2024 at 6:03 PM syzbot
> <syzbot+38a095a81f30d82884c1@...kaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    78d4f34e2115 Linux 6.13-rc3
>> git tree:       upstream
>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=16445730580000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=6c532525a32eb57d
>> dashboard link: https://syzkaller.appspot.com/bug?extid=38a095a81f30d82884c1
>> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=169b0b44580000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f502df980000
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/7129ee07f8aa/disk-78d4f34e.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/c23c0af59a16/vmlinux-78d4f34e.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/031aecf04ea7/bzImage-78d4f34e.xz
>>
>> The issue was bisected to:
>>
>> commit b83fbca1b4c9c45628aa55d582c14825b0e71c2b
>> Author: Matthieu Baerts (NGI0) <matttbe@...nel.org>
>> Date:   Mon Sep 2 10:45:53 2024 +0000
>>
>>     mptcp: pm: reduce entries iterations on connect
>>
>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=163682df980000
>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=153682df980000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=113682df980000

(...)

> I spent some time on this bug before releasing it, because I have
> other syzbot reports probably
> caused by the same issue, hinting at shinfo->nr_frags corruption.
> 
> I will hold these reports to avoid flooding the mailing list.

Thank you for having released this bug report!

The bisected commit looks unrelated. I don't know if we can tell syzbot
to "skip this commit and try harder".

I'm trying to run a 'git bisect' on my side since this morning: the
issue seems to be older, between v6.10 and v6.11 if I'm not mistaken.
When using the same kernel config, I'm getting quite a few issues on
older commits (compilation, other warnings, etc.), plus the compilation
is slow on my laptop. I will update you if I can find anything useful.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.