linux-kernel - Re: [PATCH] aio: fix io_setup/io

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Message-ID: <x49obs8uvil.fsf@segfault.boston.devel.redhat.com>
Date:	Wed, 07 Mar 2012 13:16:18 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Benjamin LaHaise <bcrl@...ck.org>,
	linux-kernel@...r.kernel.org, linux-aio@...ck.org
Subject: Re: [PATCH] aio: fix io_setup/io_destroy race

Al Viro <viro@...IV.linux.org.uk> writes:

> Have ioctx_alloc() return an extra reference, so that caller would drop it
> on success and not bother with re-grabbing it on failure exit.  The current
> code is obviously broken - io_destroy() from another thread that managed
> to guess the address io_setup() would've returned would free ioctx right
> under us; gets especially interesting if aio_context_t * we pass to
> io_setup() points to PROT_READ mapping, so put_user() fails and we end
> up doing io_destroy() on kioctx another thread has just got freed...

Al, you certainly are creative.  ;-) I agree with the problem and the
fix.  It would be nice, though if you had added comments.

I ran xfstests ./check -g aio, and there were no problems.

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
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