[PATCH 3.15 127/139] fs: btrfs: volumes.c: Fix for possible null pointer dereference

[Greg Kroah-Hartman]

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx>

commit 8321cf2596d283821acc466377c2b85bcd3422b7 upstream.

There is otherwise a risk of a possible null pointer dereference.

Was largely found by using a static code analysis program called cppcheck.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Mason <clm@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/volumes.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1690,11 +1690,12 @@ int btrfs_rm_device(struct btrfs_root *r
 		struct btrfs_fs_devices *fs_devices;
 		fs_devices = root->fs_info->fs_devices;
 		while (fs_devices) {
-			if (fs_devices->seed == cur_devices)
+			if (fs_devices->seed == cur_devices) {
+				fs_devices->seed = cur_devices->seed;
 				break;
+			}
 			fs_devices = fs_devices->seed;
 		}
-		fs_devices->seed = cur_devices->seed;
 		cur_devices->seed = NULL;
 		lock_chunks(root);
 		__btrfs_close_devices(cur_devices);


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