[PATCH 4.9 053/101] Btrfs: fix return value on rename exchange failure

From: Greg Kroah-Hartman
Date: Sun Jul 01 2018 - 14:15:47 EST

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


From: Filipe Manana <fdmanana@xxxxxxxx>

commit c5b4a50b74018b3677098151ec5f4fce07d5e6a0 upstream.

If we failed during a rename exchange operation after starting/joining a
transaction, we would end up replacing the return value, stored in the
local 'ret' variable, with the return value from btrfs_end_transaction().
So this could end up returning 0 (success) to user space despite the
operation having failed and aborted the transaction, because if there are
multiple tasks having a reference on the transaction at the time
btrfs_end_transaction() is called by the rename exchange, that function
returns 0 (otherwise it returns -EIO and not the original error value).
So fix this by not overwriting the return value on error after getting
a transaction handle.

Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
CC: stable@xxxxxxxxxxxxxxx # 4.9+
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/btrfs/inode.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9561,6 +9561,7 @@ static int btrfs_rename_exchange(struct
u64 new_idx = 0;
u64 root_objectid;
int ret;
+ int ret2;
bool root_log_pinned = false;
bool dest_log_pinned = false;

@@ -9751,7 +9752,8 @@ out_fail:
dest_log_pinned = false;
- ret = btrfs_end_transaction(trans, root);
+ ret2 = btrfs_end_transaction(trans, root);
+ ret = ret ? ret : ret2;