linux-kernel - Re: [BUG] ext4/block null pointer crashes in linux-next

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 for Android: free password hash cracker in your pocket

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

Date:   Fri, 19 Oct 2018 11:52:36 -0400
From:   valdis.kletnieks@...edu
To:     Dennis Zhou <dennis@...nel.org>
Cc:     Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [BUG] ext4/block null pointer crashes in linux-next

On Wed, 17 Oct 2018 17:20:29 -0400, Dennis Zhou said:
>
> I apologize, but I'm having a hard time reproducing this myself. I am
> not able to hit this issue in my qemu instance with linux-next built
> with your config. I have been running 'rpm -Hvh --force fio.rpm' several
> times and haven't seen the issue.

I wouldn't be surprised if there's something oddball in my system config
that changes the situation.

> Would it be possible for you to create a minimal qemu image that
> reproduces the issue as I'm having issues reproducing it with my setup?

Hmm.. I'd first have to figure out how to build a qemu image at all..

> Additionally, I've added some more debug text in the diff below. If you
> could apply that and send me the full dmesg that would be great. Lastly,
> can you just confirm for me that the commit before, f0fcb3ec89f3
> "blkcg: remove additional reference to the css", isn't seeing this
> issue?

Full dmesg attached.  Had to piece it together from a 'dmesg' and what
got saved in pstore when it crashed.  I was surprised that the printk_once
popped during very early boot (2.88 seconds in), and then only 2 lines of output
right before the crash:

[  106.465848] audit: type=1130 audit(1539957798.984:101): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:syst
em_r:init_t:s0-s15:c0.c1023 msg='unit=run-r93ac4731e4724fd6a3670e7d0c417522 comm="systemd" exe="/usr/lib/systemd/systemd
" hostname=? addr=? terminal=? res=success'
[  106.564711] dennis: q ffff9e3c57152000 != rl->q ffff9e3a8fe48040
[  106.564713] dennis: bio: ffff9e3a8fcf5400, root: ffffffffbbdd89e0
[  106.564761] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[  106.568786] PGD 0 P4D 0
[  106.570761] Oops: 0000 [#1] PREEMPT SMP PTI
[  106.573115] CPU: 2 PID: 1205 Comm: sh Tainted: G                T 4.19.0-rc8-next-20181016-dirty #639

I'll cook up a kernel checked out at that commit and test later today...

View attachment "dmesg.all" of type "text/plain " (83725 bytes)

Content of type "application/pgp-signature" skipped