ovl: Filter invalid inodes with missing lookup function

Add a check to the ovl_dentry_weird() function to prevent the
processing of directory inodes that lack the lookup function.
This is important because such inodes can cause errors in overlayfs
when passed to the lowerstack.

Reported-by: [email protected]
Link: https://syzkaller.appspot.com/bug?extid=a8c9d476508bd14a90e5
Suggested-by: Miklos Szeredi <[email protected]>
Link: https://lore.kernel.org/linux-unionfs/CAJfpegvx-oS9XGuwpJx=Xe28_jzWx5eRo1y900_ZzWY+=gGzUg@mail.gmail.com/
Signed-off-by: Vasiliy Kovalev <[email protected]>
Cc: <[email protected]>
Signed-off-by: Amir Goldstein <[email protected]>

Author: kovalev0

fs/overlayfs/util.c

@@ -202,6 +202,9 @@ void ovl_dentry_init_flags(struct dentry *dentry, struct dentry *upperdentry,
 
 bool ovl_dentry_weird(struct dentry *dentry)
 {
+	if (!d_can_lookup(dentry) && !d_is_file(dentry) && !d_is_symlink(dentry))
+		return true;
+
 	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
 				  DCACHE_MANAGE_TRANSIT |
 				  DCACHE_OP_HASH |