[PATCH 4.14 109/178] btrfs: Explicitly handle btrfs_update_root failure

From: Greg Kroah-Hartman
Date: Mon Dec 18 2017 - 11:36:51 EST

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


From: Nikolay Borisov <nborisov@xxxxxxxx>

[ Upstream commit 9417ebc8a676487c6ec8825f92fb28f7dbeb5f4b ]

btrfs_udpate_root can fail and it aborts the transaction, the correct
way to handle an aborted transaction is to explicitly end with
btrfs_end_transaction. Even now the code is correct since
btrfs_commit_transaction would handle an aborted transaction but this is
more of an implementation detail. So let's be explicit in handling
failure in btrfs_update_root.

Furthermore btrfs_commit_transaction can also fail and by ignoring it's
return value we could have left the in-memory copy of the root item in
an inconsistent state. So capture the error value which allows us to
correctly revert the RO/RW flags in case of commit failure.

Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
fs/btrfs/ioctl.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1842,8 +1842,13 @@ static noinline int btrfs_ioctl_subvol_s

ret = btrfs_update_root(trans, fs_info->tree_root,
&root->root_key, &root->root_item);
+ if (ret < 0) {
+ btrfs_end_transaction(trans);
+ goto out_reset;
+ }
+ ret = btrfs_commit_transaction(trans);

- btrfs_commit_transaction(trans);
if (ret)
btrfs_set_root_flags(&root->root_item, root_flags);