xfs: reject swapext ioctl on swapfiles

Swapfiles are magic - I/O is directly initialized by the VM without
involving the filesystem.  Swapping out extents underneath the VM thus
can cause severe problems.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index ac96ab9f70a2..e6d839bddbf0 100644
--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -79,6 +79,12 @@ xfs_swapext(
                 goto out_put_target_file;
         }
 
+        if (IS_SWAPFILE(file->f_path.dentry->d_inode) ||
+            IS_SWAPFILE(target_file->f_path.dentry->d_inode)) {
+                error = XFS_ERROR(EINVAL);
+                goto out_put_target_file;
+        }
+
         ip = XFS_I(file->f_path.dentry->d_inode);
         tip = XFS_I(target_file->f_path.dentry->d_inode);