linux-kernel - Re: [f2fs bug] infinite loop in f2fs_get_meta_page

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Message-ID: <20201007215305.GA714500@google.com>
Date:   Wed, 7 Oct 2020 14:53:05 -0700
From:   jaegeuk@...nel.org
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
        syzkaller-bugs@...glegroups.com, linux-kernel@...r.kernel.org,
        syzbot+ee250ac8137be41d7b13@...kaller.appspotmail.com
Subject: Re: [f2fs bug] infinite loop in f2fs_get_meta_page_nofail()

On 10/07, Eric Biggers wrote:
> [moved linux-fsdevel to Bcc]
> 
> On Wed, Oct 07, 2020 at 02:18:19AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    a804ab08 Add linux-next specific files for 20201006
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=17fe30bf900000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=26c1b4cc4a62ccb
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ee250ac8137be41d7b13
> > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1336413b900000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12f7392b900000
> > 
> > The issue was bisected to:
> > 
> > commit eede846af512572b1f30b34f9889d7df64c017d4
> > Author: Jaegeuk Kim <jaegeuk@...nel.org>
> > Date:   Fri Oct 2 21:17:35 2020 +0000
> > 
> >     f2fs: f2fs_get_meta_page_nofail should not be failed
> > 
> 
> Jaegeuk, it looks like the loop you added in the above commit doesn't terminate
> if the requested page is beyond the end of the device.

Yes, that will go infinite loop. Otherwise, it will trigger a panic during
the device reboot. Let me think how to avoid that before trying to get the
wrong lba access.

> 
> - Eric