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

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Message-Id: <20180701160759.265134383@linuxfoundation.org>
Date:   Sun,  1 Jul 2018 18:21:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Filipe Manana <fdmanana@...e.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 4.9 053/101] Btrfs: fix return value on rename exchange failure

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

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

From: Filipe Manana <fdmanana@...e.com>

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@...r.kernel.org # 4.9+
Signed-off-by: Filipe Manana <fdmanana@...e.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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;
 out_notrans:
 	if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
 		up_read(&dest->fs_info->subvol_sem);