From: Jan Kara <jack@suse.cz>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: syzbot <syzbot+4a03518df1e31b537066@syzkaller.appspotmail.com>,
adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com, tytso@mit.edu
Subject: Re: [syzbot] [ext4?] KCSAN: data-race in __es_find_extent_range / __es_find_extent_range (6)
Date: Wed, 3 May 2023 19:42:54 +0200 [thread overview]
Message-ID: <20230503174254.xbggzuzej6bbugts@quack3> (raw)
In-Reply-To: <CACT4Y+a20C5kUHRKbFB08QsLbdia+ELCOcKibJVY_v+xmjMPow@mail.gmail.com>
On Mon 24-04-23 09:27:00, Dmitry Vyukov wrote:
> On Mon, 24 Apr 2023 at 09:19, syzbot
> <syzbot+4a03518df1e31b537066@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 44149752e998 Merge tag 'cgroup-for-6.3-rc6-fixes' of git:/..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=100db37bc80000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=710057cbb8def08c
> > dashboard link: https://syzkaller.appspot.com/bug?extid=4a03518df1e31b537066
> > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/7bfa303f05cc/disk-44149752.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/4e8ea8730409/vmlinux-44149752.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/e584bce13ba7/bzImage-44149752.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+4a03518df1e31b537066@syzkaller.appspotmail.com
>
> The race is here:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/ext4/extents_status.c?id=44149752e9987a9eac5ad78e6d3a20934b5e018d#n271
>
> If I am reading this correctly, it can lead to returning a wrong
> extent if tree->cache_es is re-read after the range check.
> I think tree->cache_es read/write should use READ/WRITE_ONCE.
Right. I'll send a fix.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2023-05-03 17:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-24 7:19 [syzbot] [ext4?] KCSAN: data-race in __es_find_extent_range / __es_find_extent_range (6) syzbot
2023-04-24 7:27 ` Dmitry Vyukov
2023-05-03 17:42 ` Jan Kara [this message]
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