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>

diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index ac96ab9f70a22b1cd6ce94bac55d903bcb43b2c9..e6d839bddbf008b3bc522720e5f5e0711a954e10 100644 (file)
--- 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);