Btrfs: do not overwrite error return value in scrub progress ioctl

If the call to btrfs_scrub_progress() failed we would overwrite the error
returned to user space with -EFAULT if the call to copy_to_user() failed
as well. Fix that by calling copy_to_user() only if btrfs_scrub_progress()
returned success.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d34e54d80149d0b9866989b11f201a7d0f19ba2a..02ea03d220e86cd8afa9d5cd755dc7a8d957c088 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4414,7 +4414,7 @@ static long btrfs_ioctl_scrub_progress(struct btrfs_fs_info *fs_info,
 
        ret = btrfs_scrub_progress(fs_info, sa->devid, &sa->progress);
 
-       if (copy_to_user(arg, sa, sizeof(*sa)))
+       if (ret == 0 && copy_to_user(arg, sa, sizeof(*sa)))
                ret = -EFAULT;
 
        kfree(sa);