linux-kernel - Re: [PATCH 3.12 32/64] unix: properly account for FDs passed over unix sockets

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Date:	Fri, 12 Feb 2016 09:45:22 +0100
From:	Philipp Hahn <pmhahn@...ahn.de>
To:	Jiri Slaby <jslaby@...e.cz>, Willy Tarreau <w@....eu>
Cc:	stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S . Miller" <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH 3.12 32/64] unix: properly account for FDs passed over
 unix sockets

Am 12.02.2016 um 08:57 schrieb Jiri Slaby:
> On 02/11/2016, 06:32 PM, Willy Tarreau wrote:
>> On Thu, Feb 11, 2016 at 02:59:08PM +0100, Jiri Slaby wrote:
>>> From: willy tarreau <w@....eu>
>>>
>>> 3.12-stable review patch.  If anyone has any objections, please let me know.
>>>
>>> ===============
>>>
>>> [ Upstream commit 712f4aad406bb1ed67f3f98d04c044191f0ff593 ]
>>>
>>> It is possible for a process to allocate and accumulate far more FDs than
>>> the process' limit by sending them over a unix socket then closing them
>>> to keep the process' fd count low.
>>>
>>> This change addresses this problem by keeping track of the number of FDs
>>> in flight per user and preventing non-privileged processes from having
>>> more FDs in flight than their configured FD limit.
>>>
>>> Reported-by: socketpair@...il.com
>>> Reported-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
>>> Mitigates: CVE-2013-4312 (Linux 2.0+)
>>> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
>>> Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
>>> Signed-off-by: Willy Tarreau <w@....eu>
>>> Signed-off-by: David S. Miller <davem@...emloft.net>
>>> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
>>
>> A possible issue was reported regarding this patch, and Hannes
>> implemented a fix that's not yet in mainline. I guess it's
>> preferable to postpone this patch for now.
> 
> yes definitely. Thanks for noting.

Yes and no: the above mentioned patch looks innocent now after more
bisecting, but there is <https://patchwork.ozlabs.org/patch/577653/> as
a folow-up to the FD-accounting.

> For reference:
> http://article.gmane.org/gmane.linux.kernel/2142236

Better read the full thread:
<http://thread.gmane.org/gmane.linux.kernel/2142236>; the suspected bad
patch is
 unix: avoid use-after-free in ep_remove_wait_queue

Philipp