[RFC v2 3/4] ext4: add verifier check for symlink with append/immutable flags

[Luis R. Rodriguez]

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 <mcg...@kernel.org>
---
 fs/ext4/inode.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 37a2f7a2b66a..6acf0dd6b6e6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4947,6 +4947,13 @@ 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);
-- 
2.17.0