linux-kernel - Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in __getblk

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Date: Wed, 31 Jan 2024 11:56:22 +0100
From: Christian Brauner <brauner@...nel.org>
To: Jan Kara <jack@...e.cz>
Cc: syzbot <syzbot+69b40dc5fd40f32c199f@...kaller.appspotmail.com>, 
	akpm@...ux-foundation.org, axboe@...nel.dk, chenzhongjin@...wei.com, dchinner@...hat.com, 
	hch@...radead.org, hch@....de, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, penguin-kernel@...ove.sakura.ne.jp, 
	syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk, willy@...radead.org
Subject: Re: [syzbot] [fs?] BUG: sleeping function called from invalid
 context in __getblk_gfp

On Tue, Jan 30, 2024 at 12:54:30PM +0100, Jan Kara wrote:
> On Mon 29-01-24 17:15:05, syzbot wrote:
> > syzbot suspects this issue was fixed by commit:
> > 
> > commit 6f861765464f43a71462d52026fbddfc858239a5
> > Author: Jan Kara <jack@...e.cz>
> > Date:   Wed Nov 1 17:43:10 2023 +0000
> > 
> >     fs: Block writes to mounted block devices
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=116642dfe80000
> > start commit:   d88520ad73b7 Merge tag 'pull-nfsd-fix' of git://git.kernel..
> > git tree:       upstream
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=174a257c5ae6b4fd
> > dashboard link: https://syzkaller.appspot.com/bug?extid=69b40dc5fd40f32c199f
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16a77593680000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1104a593680000
> > 
> > If the result looks correct, please mark the issue as fixed by replying with:
> > 
> > #syz fix: fs: Block writes to mounted block devices
> 
> This doesn't look correct. The problem here really is that sysv is calling
> sb_bread() under a RWLOCK - pointers_lock - in get_block(). Which more or
> less shows nobody has run sysv in ages because otherwise the chances of
> sleeping in atomic context are really high? Perhaps another candidate for
> removal?

Fwiw, yes, please!