linux-kernel - Re: [PATCH] kmod: Fix race in usermodehelper code

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]

Date:	Wed, 1 Jul 2009 13:56:31 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Neil Horman <nhorman@...driver.com>
Cc:	linux-kernel@...r.kernel.org, nhorman@...driver.com,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH] kmod: Fix race in usermodehelper code

On Tue, 30 Jun 2009 22:48:03 -0400
Neil Horman <nhorman@...driver.com> wrote:

> User Mode Helper: Fix race in UMH_WAIT_EXEC case
> 
> The user mode helper code has a race in it.  call_usermodehelper_exec takes an
> allocated subprocess_info structure, which it passes to a workqueue, and then
> passes it to a kernel thread which it creates, after which it calls complete to
> signal to the caller of call_usremodehelper_exec that it can free the
> subprocess_info struct.  But since we use that structure in the created thread,
> we can't call complete from __call_usermodehelper, which is where we create the
> kernel_thread.  We need to call complete from within the kernel thread and then
> not use subprocess_info afterward in the case of UMH_WAIT_EXEC.  Tested
> successfully by me.
> 

<stares at the code for ten minutes>

Geeze that's getting complex, isn't it?  The patch looks OK.  I think.

I wonder why people aren't reporting this.  Perhaps CLONE_VFORK plus
child-runs-first?  (_does_ the chld run first?  We seem to have changed
it a couple of times)


--
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/