From 977b3754117963d8a551ea16f14f45506e8b7e79 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Fri, 10 Jul 2009 03:27:40 +0200
Subject: [PATCH] --- yaml --- r: 157324 b: refs/heads/master c:
 896a6de40ef3814525632609799af909338f50c3 h: refs/heads/master v: v3

---
 [refs]               |  2 +-
 trunk/fs/proc/base.c | 22 +++++++++++-----------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/[refs] b/[refs]
index 124856dcbfef..1fc603748ab8 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d3c8660233d3f2801e14eaf722937ff4ed49bfb7
+refs/heads/master: 896a6de40ef3814525632609799af909338f50c3
diff --git a/trunk/fs/proc/base.c b/trunk/fs/proc/base.c
index f3c2e4085fed..175db258942f 100644
--- a/trunk/fs/proc/base.c
+++ b/trunk/fs/proc/base.c
@@ -234,19 +234,19 @@ static int check_mem_permission(struct task_struct *task)
 
 struct mm_struct *mm_for_maps(struct task_struct *task)
 {
-	struct mm_struct *mm = get_task_mm(task);
+	struct mm_struct *mm;
 
-	if (mm && mm != current->mm) {
-		/*
-		 * task->mm can be changed before security check,
-		 * in that case we must notice the change after.
-		 */
-		if (!ptrace_may_access(task, PTRACE_MODE_READ) ||
-		    mm != task->mm) {
-			mmput(mm);
-			mm = NULL;
-		}
+	if (mutex_lock_killable(&task->cred_guard_mutex))
+		return NULL;
+
+	mm = get_task_mm(task);
+	if (mm && mm != current->mm &&
+			!ptrace_may_access(task, PTRACE_MODE_READ)) {
+		mmput(mm);
+		mm = NULL;
 	}
+	mutex_unlock(&task->cred_guard_mutex);
+
 	return mm;
 }