btrfs: fix transaction leak in btrfs_recover_relocation

commit 1402d17dfd9657be0da8458b2079d03c2d61c86a upstream.

btrfs_recover_relocation() invokes btrfs_join_transaction(), which joins
a btrfs_trans_handle object into transactions and returns a reference of
it with increased refcount to "trans".

When btrfs_recover_relocation() returns, "trans" becomes invalid, so the
refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
btrfs_recover_relocation(). When read_fs_root() failed, the refcnt
increased by btrfs_join_transaction() is not decreased, causing a refcnt
leak.

Fix this issue by calling btrfs_end_transaction() on this error path
when read_fs_root() failed.

Fixes: 79787eaab461 ("btrfs: replace many BUG_ONs with proper error handling")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit a378abbb8e394f30e97b243a018f9135b39abc96)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 2fb429426f96f4912c7926cc92a6787c86fef881..721259d8ab649822d87ee795d847578269617105 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4640,6 +4640,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
                if (IS_ERR(fs_root)) {
                        err = PTR_ERR(fs_root);
                        list_add_tail(&reloc_root->root_list, &reloc_roots);
+                       btrfs_end_transaction(trans);
                        goto out_unset;
                }