[PATCH 4.5 119/128] btrfs: add write protection to SET_FEATURES ioctl

Greg Kroah-Hartman
2016-06-06T14:35:40Z

From: David Sterba <dsterba@suse.cz>

commit 7ab19625a911f7568ec85302e3aa7a64186006c8 upstream.

Perform the want_write check if we get far enough to do any writes.

Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/ioctl.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5397,9 +5397,15 @@ static int btrfs_ioctl_set_features(stru
if (ret)
return ret;

+ ret = mnt_want_write_file(file);
+ if (ret)
+ return ret;
+
trans = btrfs_start_transaction(root, 0);
- if (IS_ERR(trans))
- return PTR_ERR(trans);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ goto out_drop_write;
+ }

spin_lock(&root->fs_info->super_lock);
newflags = btrfs_super_compat_flags(super_block);
@@ -5418,7 +5424,11 @@ static int btrfs_ioctl_set_features(stru
btrfs_set_super_incompat_flags(super_block, newflags);
spin_unlock(&root->fs_info->super_lock);

- return btrfs_commit_transaction(trans, root);
+ ret = btrfs_commit_transaction(trans, root);
+out_drop_write:
+ mnt_drop_write_file(file);
+
+ return ret;
}

long btrfs_ioctl(struct file *file, unsigned int