ext4: add verifier check for symlink with append/immutable flags

The Linux VFS does not allow a way to set append/immuttable
attributes to symlinks, this is just not possible. If this is
detected inform the user as the filesystem must be corrupted.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0eb64e8f9602..9d512fa80d28 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4965,6 +4965,13 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
                 inode->i_op = &ext4_dir_inode_operations;
                 inode->i_fop = &ext4_dir_operations;
         } else if (S_ISLNK(inode->i_mode)) {
+                /* VFS does not allow setting these so must be corruption */
+                if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
+                        EXT4_ERROR_INODE(inode,
+                          "immutable or append flags not allowed on symlinks");
+                        ret = -EFSCORRUPTED;
+                        goto bad_inode;
+                }
                 if (ext4_encrypted_inode(inode)) {
                         inode->i_op = &ext4_encrypted_symlink_inode_operations;
                         ext4_set_aops(inode);