ext4: Make sure the MOVE_EXT ioctl can't overwrite append-only files

Dan Roseberg has reported a problem with the MOVE_EXT ioctl.  If the
donor file is an append-only file, we should not allow the operation
to proceed, lest we end up overwriting the contents of an append-only
file.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Dan Rosenberg <dan.j.rosenberg@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 3a6c92ac131c..52abfa12762a 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -960,6 +960,9 @@ mext_check_arguments(struct inode *orig_inode,
                 return -EINVAL;
         }
 
+        if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
+                return -EPERM;
+
         /* Ext4 move extent does not support swapfile */
         if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
                 ext4_debug("ext4 move extent: The argument files should "