btrfs: array overflow in btrfs_ioctl_rm_dev_v2()

We were putting the NUL terminator at BTRFS_PATH_NAME_MAX (4087) bytes instead of BTRFS_SUBVOL_NAME_MAX (4039) so it corrupted memory.

Fixes 22af1a869288 ('btrfs: introduce device delete by devid')

Signed-off-by Dan Carpenter <[email protected]>

fs/btrfs/ioctl.c +1 -2

index 5224fc8..77c61b4 100644
@@ -2700,7 +2700,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
  	if (vol_args->flags & BTRFS_DEVICE_SPEC_BY_ID) {
  		ret = btrfs_rm_device(root, NULL, vol_args->devid);
  	} else {
-		vol_args->name[BTRFS_PATH_NAME_MAX] = '\0';
+		vol_args->name[BTRFS_SUBVOL_NAME_MAX] = '\0';
  		ret = btrfs_rm_device(root, vol_args->name, 0);
  	}
  	mutex_unlock(&root->fs_info->volume_mutex);
--

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Thanks Dan.
Chris pointed out as well. We are working on it..

Just one concern when device is added the max device length is BTRFS_PATH_NAME_MAX. However below fix is proper from the vol_args perspective.