From: Li Zefan <lizefan@huawei.com>
Date: Fri, 25 Jan 2013 08:08:01 +0000 (+0800)
Subject: cpuset: fix cpuset_print_task_mems_allowed() vs rename() race
X-Git-Tag: v3.2.40~85
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=59222bdd5b2a0e4f868d867a71397945236c1412;p=thirdparty%2Fkernel%2Fstable.git

cpuset: fix cpuset_print_task_mems_allowed() vs rename() race

commit 63f43f55c9bbc14f76b582644019b8a07dc8219a upstream.

rename() will change dentry->d_name. The result of this race can
be worse than seeing partially rewritten name, but we might access
a stale pointer because rename() will re-allocate memory to hold
a longer name.

It's safe in the protection of dentry->d_lock.

v2: check NULL dentry before acquiring dentry lock.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 84a524bba1060..835eee6a287b6 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2507,8 +2507,16 @@ void cpuset_print_task_mems_allowed(struct task_struct *tsk)
 
 	dentry = task_cs(tsk)->css.cgroup->dentry;
 	spin_lock(&cpuset_buffer_lock);
-	snprintf(cpuset_name, CPUSET_NAME_LEN,
-		 dentry ? (const char *)dentry->d_name.name : "/");
+
+	if (!dentry) {
+		strcpy(cpuset_name, "/");
+	} else {
+		spin_lock(&dentry->d_lock);
+		strlcpy(cpuset_name, (const char *)dentry->d_name.name,
+			CPUSET_NAME_LEN);
+		spin_unlock(&dentry->d_lock);
+	}
+
 	nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN,
 			   tsk->mems_allowed);
 	printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n",