From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932468Ab1EFAZ4 (ORCPT ); Thu, 5 May 2011 20:25:56 -0400 Received: from kroah.org ([198.145.64.141]:37276 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932406Ab1EFAZx (ORCPT ); Thu, 5 May 2011 20:25:53 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Thu May 5 17:22:17 2011 Message-Id: <20110506002217.060207898@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Thu, 05 May 2011 17:21:45 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Eric Dumazet , "David S. Miller" Subject: [120/143] af_unix: limit unix_tot_inflight In-Reply-To: <20110506002311.GA15354@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Eric Dumazet commit 9915672d41273f5b77f1b3c29b391ffb7732b84b upstream. Vegard Nossum found a unix socket OOM was possible, posting an exploit program. My analysis is we can eat all LOWMEM memory before unix_gc() being called from unix_release_sock(). Moreover, the thread blocked in unix_gc() can consume huge amount of time to perform cleanup because of huge working set. One way to handle this is to have a sensible limit on unix_tot_inflight, tested from wait_for_unix_gc() and to force a call to unix_gc() if this limit is hit. This solves the OOM and also reduce overall latencies, and should not slowdown normal workloads. Reported-by: Vegard Nossum Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/unix/garbage.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -269,9 +269,16 @@ static void inc_inflight_move_tail(struc } static bool gc_in_progress = false; +#define UNIX_INFLIGHT_TRIGGER_GC 16000 void wait_for_unix_gc(void) { + /* + * If number of inflight sockets is insane, + * force a garbage collect right now. + */ + if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress) + unix_gc(); wait_event(unix_gc_wait, gc_in_progress == false); }