linux-kernel - Re: [PATCH -v2] fix for futex

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Date:	Wed, 5 Dec 2007 06:54:09 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	David Holmes - Sun Microsystems <David.Holmes@....COM>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stable Team <stable@...nel.org>
Subject: Re: [PATCH -v2] fix for futex_wait signal stack corruption

On Tue, 4 Dec 2007, Linus Torvalds wrote:
> 
> Patch looks fine to me.
> 
> On Tue, 4 Dec 2007, Steven Rostedt wrote:
> > 
> > Note: I'm a bit nervious to add "linux/types.h" and use u32 and u64
> > in thread_info.h, when there's a #ifdef __KERNEL__ just below that.
> > Not sure what that is there for.
> 
> Hmm. I'd not expect user-mode headers to ever include 
> <linux/thread-info.h>, and if they do, they'd already get get totally 
> invalid namespace pollution ("struct restart_block" at a minimum) along 
> with stuff that simply isn't sensible in user-space at all, so I think 
> this part is fine.
> 
> And I guess somebody will scream if it bites them ;)
> 
> Anyway, my gut feel is that this is potentially a real problem, and we 
> should fix it asap (ie it should go into 2.6.24 even at this late stage in 
> the game), but it would be nice to know if the problem actually hit any 
> actual real program, and not just a test-setup.
> 
> So here's a question for David Holmes:  What caused you to actually notice 
> this behaviour? Can this actually be seen in real life usage?
> 
> Anyway, at a minimum, here's an
> 
> 	Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
> 
> and I suspect I should just apply it directly. Any comments from anybody 
> else?

Doh, yes. I completely missed that stack dependency of the pointer
when I looked at the patch back then. The solution looks solid and
probably we should get rid of the unnamed union member and fixup the
other places which use restart_block in a similar way.

Just a minor nit. Can we please use "futex" instead of "fu" ? I'm just
envisioning the next union member named "ba".

Acked-by: Thomas Gleixner <tglx@...utronix.de>

Please apply with the s/fu/futex/ change. This needs to go into stable
.22/.23 as well.

Thanks,

	tglx
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