linux-kernel - Re: [PATCH] kthread: Enhance kthread_stop to abort interruptible sleeps

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: <20070424030924.be44ebfa.akpm@linux-foundation.org>
Date:	Tue, 24 Apr 2007 03:09:24 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	Oleg Nesterov <oleg@...sign.ru>,
	Davide Libenzi <davidel@...ilserver.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Roland McGrath <roland@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] kthread: Enhance kthread_stop to abort interruptible
 sleeps

On Fri, 13 Apr 2007 21:13:13 -0600 ebiederm@...ssion.com (Eric W. Biederman) wrote:

> This patch reworks kthread_stop so it is more flexible and it causes
> the target kthread to abort interruptible sleeps.  Allowing a larger
> class of kernel threads to use to the kthread API.
> 
> The changes start by defining TIF_KTHREAD_STOP on all architectures.
> TIF_KTHREAD_STOP is a per process flag that I can set from another
> process to indicate that a kernel thread should stop.
> 
> wake_up_process in kthread_stop has been replaced by signal_wake_up
> ensuring that the kernel thread if sleeping is woken up in a timely
> manner and with TIF_SIGNAL_PENDING set, which causes us to break out
> of interruptible sleeps.
> 
> recalc_signal_pending was modified to keep TIF_SIGNAL_PENDING set for
> as long as TIF_KTHREAD_STOP is set.
> 
> Arbitrary paths to do_exit are now allowed.  I have placed a
> completion on the thread stack and pointed vfork_done at it, when the
> mm_release is called from do_exit the completion will be called.
> Since the completion is stored on the stack it is important that
> kthread() now calls do_exit ensuring the stack frame that holds the
> completion is never released, and so that our exit_code is certain to
> make it unchanged all the way to do_exit.
> 
> To allow kthread_stop to read the process exit code when exit_mm wakes
> it up  I have moved the setting of exit_code to the beginning of
> do_exit. 

This patch causes this oops: http://userweb.kernel.org/~akpm/s5000508.jpg
with this config: http://userweb.kernel.org/~akpm/config-x.txt
-
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/