linux-kernel - Re: [syzbot] [udf?] BUG: unable to handle kernel NULL pointer dereference in _

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230123073609.GA31134@lst.de>
Date:   Mon, 23 Jan 2023 08:36:09 +0100
From:   Christoph Hellwig <hch@....de>
To:     syzbot <syzbot+c27475eb921c46bbdc62@...kaller.appspotmail.com>
Cc:     akpm@...ux-foundation.org, hch@....de, jack@...e.com, jack@...e.cz,
        linkinjeon@...il.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com, willy@...radead.org
Subject: Re: [syzbot] [udf?] BUG: unable to handle kernel NULL pointer
 dereference in __writepage

I looked into this and got really confused.  We should never end
up in generic_writepages if ->writepages is set, which this patch
obviously does.

Then I took a closer look at udf, and it seems to switch a_aops around
at run time, and it seems like we're hitting just that case, and the
patch just seems to narrow down that window.

I suspect the right fix is to remove this runtime switching of aops,
and just do conditionals inside the methods.