From: Wang YanQing <udknight@gmail.com>
Date: Tue, 23 Jun 2015 10:54:45 +0000 (+0800)
Subject: fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=1af95de6f0119d5bde02d3a811a9f3a3661e954e;p=deliverable%2Flinux.git

fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation

Execution of get_anon_bdev concurrently and preemptive kernel all
could bring race condition, it isn't enough to check dev against
its upper limitation with equality operator only.

This patch fix it.

Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/super.c b/fs/super.c
index 928c20f47af9..b61372354f2b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -842,7 +842,7 @@ int get_anon_bdev(dev_t *p)
 	else if (error)
 		return -EAGAIN;
 
-	if (dev == (1 << MINORBITS)) {
+	if (dev >= (1 << MINORBITS)) {
 		spin_lock(&unnamed_dev_lock);
 		ida_remove(&unnamed_dev_ida, dev);
 		if (unnamed_dev_start > dev)