From: Pavel Skripkin <paskripkin@gmail.com>
To: Matthieu Baerts <matthieu.baerts@tessares.net>,
syzbot <syzbot+7b938780d5deeaaf938f@syzkaller.appspotmail.com>,
davem@davemloft.net, johan.hedberg@gmail.com, kuba@kernel.org,
linux-bluetooth@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, luiz.dentz@gmail.com,
marcel@holtmann.org, mathew.j.martineau@linux.intel.com,
netdev@vger.kernel.org, pabeni@redhat.com,
syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk
Subject: Re: [syzbot] KFENCE: use-after-free in kvm_fastop_exception
Date: Wed, 18 Aug 2021 11:12:14 +0300 [thread overview]
Message-ID: <6736a510-20a1-9fb5-caf4-86334cabbbb6@gmail.com> (raw)
In-Reply-To: <58cef9e0-69de-efdb-4035-7c1ed3d23132@tessares.net>
On 8/18/21 11:02 AM, Matthieu Baerts wrote:
> Hello,
>
> On 18/08/2021 00:21, syzbot wrote:
>> syzbot has bisected this issue to:
>>
>> commit c4512c63b1193c73b3f09c598a6d0a7f88da1dd8
>> Author: Matthieu Baerts <matthieu.baerts@tessares.net>
>> Date: Fri Jun 25 21:25:22 2021 +0000
>>
>> mptcp: fix 'masking a bool' warning
>>
>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=122b0655300000
>> start commit: b9011c7e671d Add linux-next specific files for 20210816
>> git tree: linux-next
>> final oops: https://syzkaller.appspot.com/x/report.txt?x=112b0655300000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=162b0655300000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=a245d1aa4f055cc1
>> dashboard link: https://syzkaller.appspot.com/bug?extid=7b938780d5deeaaf938f
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=157a41ee300000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14f78ff9300000
>
> I'm pretty sure the commit c4512c63b119 ("mptcp: fix 'masking a bool'
> warning") doesn't introduce the reported bug. This minor fix is specific
> to MPTCP which doesn't seem to be used here.
>
> I'm not sure how I can tell syzbot this is a false positive.
>
looks like it's fs/namei bug. Similar reports:
https://syzkaller.appspot.com/bug?id=517fa734b92b7db404c409b924cf5c997640e324
https://syzkaller.appspot.com/bug?id=484483daf3652b40dae18531923aa9175d392a4d
It's not false positive. I've suggested the fix here:
https://groups.google.com/g/syzkaller-bugs/c/HE3c2fP5nic/m/1Yk17GBeAwAJ
I am waiting for author comments about the fix :)
But, yes, syzbot bisection is often wrong, so don't rely on it much :)
With regards,
Pavel Skripkin
next prev parent reply other threads:[~2021-08-18 8:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 8:27 [syzbot] KFENCE: use-after-free in kvm_fastop_exception syzbot
2021-08-16 22:01 ` syzbot
2021-08-17 22:21 ` syzbot
2021-08-18 8:02 ` Matthieu Baerts
2021-08-18 8:12 ` Pavel Skripkin [this message]
2021-08-18 8:21 ` Matthieu Baerts
2021-08-18 8:55 ` Pavel Skripkin
2021-08-18 8:57 ` Matthieu Baerts
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6736a510-20a1-9fb5-caf4-86334cabbbb6@gmail.com \
--to=paskripkin@gmail.com \
--cc=davem@davemloft.net \
--cc=johan.hedberg@gmail.com \
--cc=kuba@kernel.org \
--cc=linux-bluetooth@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luiz.dentz@gmail.com \
--cc=marcel@holtmann.org \
--cc=mathew.j.martineau@linux.intel.com \
--cc=matthieu.baerts@tessares.net \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=syzbot+7b938780d5deeaaf938f@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).