linux-kernel - Re: [syzbot] kernel BUG in assertfail

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Date:   Mon, 31 May 2021 11:44:12 +0300
From:   Nikolay Borisov <nborisov@...e.com>
To:     syzbot <syzbot+a6bf271c02e4fe66b4e4@...kaller.appspotmail.com>,
        clm@...com, dsterba@...e.com, josef@...icpanda.com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] kernel BUG in assertfail



On 31.05.21 г. 10:53, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    1434a312 Merge branch 'for-5.13-fixes' of git://git.kernel..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=162843f3d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9f3da44a01882e99
> dashboard link: https://syzkaller.appspot.com/bug?extid=a6bf271c02e4fe66b4e4
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+a6bf271c02e4fe66b4e4@...kaller.appspotmail.com
> 
> assertion failed: !memcmp(fs_info->fs_devices->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE), in fs/btrfs/disk-io.c:3282

This means a device contains a btrfs filesystem which has a different
FSID in its superblock than the fsid which all devices part of the same
fs_devices should have. This can happen in 2 ways - memory corruption
where either of the ->fsid member are corrupted or if there was a crash
while a filesystem's fsid was being changed. We need more context about
what the test did?