linux-kernel - Crash in schedule path after worker thread dies

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-next>] [day] [month] [year] [list]

Date:	Tue, 19 Jul 2011 17:07:38 -0700
From:	Todd Poynor <toddpoynor@...gle.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Crash in schedule path after worker thread dies

After a worker thread died due to a bug in a work function, a NULL
dereference was seen when schedule calls wq_worker_sleeping calls
kthread_data:

          return to_kthread(task)->data;

mm_release has apparently already set the task's vfork_done = NULL,
causing to_kthread to return a bad address (on 3.0-rc7 on ARM).

I haven't tried a fix because I'm not sure if avoiding this case is
enough to properly recover from death of a worker thread, or if this
has already been discussed and rejected in the past.  I searched
around a little and found some mentions of problems in worker
functions that were probably followed by the kthread_data crash,
but didn't turn up any specific discussion of this crash.  So I
thought I'd start by mentioning this here, and can help fix or test if
needed.

Todd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/