From 8d1ffc0f13fc683ff86ba0254afba9b99565fab7 Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba@suse.cz>
Date: Thu, 29 Sep 2011 13:11:33 +0200
Subject: [PATCH] --- yaml --- r: 274675 b: refs/heads/master c:
 f9d9ef62cd3ecbd6cbb7957a253c1e81f69d5586 h: refs/heads/master i:   274673:
 0580bef50b1e648356dc29d31626ad0d5c55cfe7   274671:
 d57bc7702e49c453a59259a3f6a52d34aa00aa42 v: v3

---
 [refs]                 |  2 +-
 trunk/fs/btrfs/super.c | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 790c0dc5fb2c..6f585509d58e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 20bcd64934e4eb8f3f90a0dca54fb0ac2edd7795
+refs/heads/master: f9d9ef62cd3ecbd6cbb7957a253c1e81f69d5586
diff --git a/trunk/fs/btrfs/super.c b/trunk/fs/btrfs/super.c
index 29eecbb6ec3a..5429b1fa0bfc 100644
--- a/trunk/fs/btrfs/super.c
+++ b/trunk/fs/btrfs/super.c
@@ -740,6 +740,16 @@ static int btrfs_set_super(struct super_block *s, void *data)
 	return set_anon_super(s, data);
 }
 
+/*
+ * subvolumes are identified by ino 256
+ */
+static inline int is_subvolume_inode(struct inode *inode)
+{
+	if (inode && inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
+		return 1;
+	return 0;
+}
+
 /*
  * This will strip out the subvol=%s argument for an argument string and add
  * subvolid=0 to make sure we get the actual tree root for path walking to the
@@ -843,6 +853,15 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags,
 	if (error)
 		return ERR_PTR(error);
 
+	if (!is_subvolume_inode(path.dentry->d_inode)) {
+		path_put(&path);
+		mntput(mnt);
+		error = -EINVAL;
+		printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n",
+				subvol_name);
+		return ERR_PTR(-EINVAL);
+	}
+
 	/* Get a ref to the sb and the dentry we found and return it */
 	s = path.mnt->mnt_sb;
 	atomic_inc(&s->s_active);