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Date: Wed, 15 May 2024 18:00:54 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: David Sterba <dsterba@suse.cz>
Cc: syzbot <syzbot+c92c93d1f1aaaacdb9db@syzkaller.appspotmail.com>,
	axboe@kernel.dk, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, maz@kernel.org, oleg@redhat.com,
	peterz@infradead.org, syzkaller-bugs@googlegroups.com
Subject: Re: kernel BUG at fs/inode.c:LINE! (2)
Message-ID: <20240515170054.GM2118490@ZenIV>
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 <20240515161314.GO4449@twin.jikos.cz>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Wed, May 15, 2024 at 06:13:14PM +0200, David Sterba wrote:
> On Fri, Aug 28, 2020 at 06:18:17AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    d012a719 Linux 5.9-rc2
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15aa650e900000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=891ca5711a9f1650
> > dashboard link: https://syzkaller.appspot.com/bug?extid=c92c93d1f1aaaacdb9db
> > compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12ecb939900000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=140a19a9900000
> > 
> > The issue was bisected to:
> > 
> > commit a9ed4a6560b8562b7e2e2bed9527e88001f7b682
> > Author: Marc Zyngier <maz@kernel.org>
> > Date:   Wed Aug 19 16:12:17 2020 +0000
> > 
> >     epoll: Keep a reference on files added to the check list
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16a50519900000
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=15a50519900000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=11a50519900000
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+c92c93d1f1aaaacdb9db@syzkaller.appspotmail.com
> > Fixes: a9ed4a6560b8 ("epoll: Keep a reference on files added to the check list")
> > 
> > ------------[ cut here ]------------
> > kernel BUG at fs/inode.c:1668!
> 
> #syz set subsystem: fs
> 
> This has been among btrfs bugs but this is is 'fs' and probably with a
> fix but I was not able to identify it among all the changes in
> eventpoll.c

It has nothing to do with btrfs, and there's a good chance it had been
fixed as a side effect of 319c15174757 "epoll: take epitem list out of struct file"
merge at 1a825a6a0e7e in 5.10 merge window; IOW, it should be in 5.11-rc1.