From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 1C5218D0039 for ; Wed, 26 Jan 2011 19:59:52 -0500 (EST) Received: from m3.gw.fujitsu.co.jp (unknown [10.0.50.73]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 466F93EE0C0 for ; Thu, 27 Jan 2011 09:59:50 +0900 (JST) Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 30F4545DE55 for ; Thu, 27 Jan 2011 09:59:50 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id EAF8745DE57 for ; Thu, 27 Jan 2011 09:59:49 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id DD1BDE08002 for ; Thu, 27 Jan 2011 09:59:49 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 95AD01DB8038 for ; Thu, 27 Jan 2011 09:59:49 +0900 (JST) Date: Thu, 27 Jan 2011 09:53:42 +0900 From: KAMEZAWA Hiroyuki Subject: [BUGFIX] memcg: fix res_counter_read_u64 lock aware (Was Re: [PATCH] oom: handle overflow in mem_cgroup_out_of_memory() Message-Id: <20110127095342.3d81cf5f.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20110127092434.df18c7a6.kamezawa.hiroyu@jp.fujitsu.com> References: <1296030555-3594-1-git-send-email-gthelen@google.com> <20110126170713.GA2401@cmpxchg.org> <20110126183023.GB2401@cmpxchg.org> <20110126142909.0b710a0c.akpm@linux-foundation.org> <20110127092434.df18c7a6.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Andrew Morton , Greg Thelen , Johannes Weiner , David Rientjes , KOSAKI Motohiro , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Thu, 27 Jan 2011 09:24:34 +0900 KAMEZAWA Hiroyuki wrote: > > > I'll review. Against the roll-over, I think we just need to take lock. > So, res_counter_read_u64() implementation was wrong. It should take lock. > Please give me time. > As far as I can see usages of return value of res_counter_read_u64() in memcontrol.c, all values are handle in u64 and no >> PAGE_SHIFT to 'int' is not done. I'll see usage of u64 return value to functions in other files from memcontrol.c But, at least, this patch is required, I think. There are races. == res_counter_read_u64 reads u64 value without lock. It's dangerous in 32bit environment. This patch adds lock. Signed-off-by: KAMEZAWA Hiroyuki --- include/linux/res_counter.h | 13 ++++++++++++- kernel/res_counter.c | 2 +- 2 files changed, 13 insertions(+), 2 deletions(-) Index: mmotm-0125/include/linux/res_counter.h =================================================================== --- mmotm-0125.orig/include/linux/res_counter.h +++ mmotm-0125/include/linux/res_counter.h @@ -68,7 +68,18 @@ struct res_counter { * @pos: and the offset. */ -u64 res_counter_read_u64(struct res_counter *counter, int member); +u64 res_counter_read_u64_locked(struct res_counter *counter, int member); + +static inline u64 res_counter_read_u64(struct res_counter *counter, int member) +{ + unsigned long flags; + u64 ret; + + spin_lock_irqsave(&counter->lock, flags); + ret = res_counter_read_u64_locked(counter, member); + spin_unlock_irqrestore(&counter->lock, flags); + return ret; +} ssize_t res_counter_read(struct res_counter *counter, int member, const char __user *buf, size_t nbytes, loff_t *pos, Index: mmotm-0125/kernel/res_counter.c =================================================================== --- mmotm-0125.orig/kernel/res_counter.c +++ mmotm-0125/kernel/res_counter.c @@ -126,7 +126,7 @@ ssize_t res_counter_read(struct res_coun pos, buf, s - buf); } -u64 res_counter_read_u64(struct res_counter *counter, int member) +u64 res_counter_read_u64_locked(struct res_counter *counter, int member) { return *res_counter_member(counter, member); } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org