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

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Message-ID: <20240130115430.rljjwjcji3vlrgyz@quack3>
Date: Tue, 30 Jan 2024 12:54:30 +0100
From: Jan Kara <jack@...e.cz>
To: syzbot <syzbot+69b40dc5fd40f32c199f@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, axboe@...nel.dk, brauner@...nel.org,
	chenzhongjin@...wei.com, dchinner@...hat.com, hch@...radead.org,
	hch@....de, jack@...e.cz, 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 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?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR