From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id BED926B02AA for ; Thu, 19 Aug 2010 11:26:27 -0400 (EDT) From: David Howells Subject: [PATCH] oom: __task_cred() need rcu_read_lock() Date: Thu, 19 Aug 2010 16:26:18 +0100 Message-ID: <20100819152618.21246.68223.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: torvalds@osdl.org, akpm@linux-foundation.org Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, rientjes@google.com, kamezawa.hiroyu@jp.fujitsu.com, KOSAKI Motohiro , David Howells List-ID: From: KOSAKI Motohiro dump_tasks() needs to hold the RCU read lock around its access of the target task's UID. To this end it should use task_uid() as it only needs that one thing from the creds. The fact that dump_tasks() holds tasklist_lock is insufficient to prevent the target process replacing its credentials on another CPU. Then, this patch change to call rcu_read_lock() explicitly. =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- mm/oom_kill.c:410 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 4 locks held by kworker/1:2/651: #0: (events){+.+.+.}, at: [] process_one_work+0x137/0x4a0 #1: (moom_work){+.+...}, at: [] process_one_work+0x137/0x4a0 #2: (tasklist_lock){.+.+..}, at: [] out_of_memory+0x164/0x3f0 #3: (&(&p->alloc_lock)->rlock){+.+...}, at: [] find_lock_task_mm+0x2e/0x70 Signed-off-by: KOSAKI Motohiro Signed-off-by: David Howells --- mm/oom_kill.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 5014e50..7b03102 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -372,7 +372,7 @@ static void dump_tasks(const struct mem_cgroup *mem) } pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n", - task->pid, __task_cred(task)->uid, task->tgid, + task->pid, task_uid(task), task->tgid, task->mm->total_vm, get_mm_rss(task->mm), task_cpu(task), task->signal->oom_adj, task->signal->oom_score_adj, task->comm); -- 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/ . Don't email: email@kvack.org