[PATCH] ovl: Add check for missing lookup operation on inode

[Vasiliy Kovalev <kovalev@altlinux.org>]

Ensure that the lookup operation is present for the inode in the overlay
filesystem. If the operation is missing, log a warning and return an EIO
error to prevent further issues in the lookup process.

Reported-by: syzbot+a8c9d476508bd14a90e5@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=a8c9d476508bd14a90e5
Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
---
 fs/overlayfs/namei.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 5764f91d283e7..a73f37e401cf0 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -1115,6 +1115,13 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	for (i = 0; !d.stop && i < ovl_numlower(poe); i++) {
 		struct ovl_path lower = ovl_lowerstack(poe)[i];
 
+		if (!lower.dentry->d_inode->i_op->lookup) {
+			err = -EIO;
+			pr_warn_ratelimited("missing lookup operation for inode %p\n",
+								lower.dentry->d_inode);
+			goto out_put;
+		}
+
 		if (!ovl_redirect_follow(ofs))
 			d.last = i == ovl_numlower(poe) - 1;
 		else if (d.is_dir || !ofs->numdatalayer)
-- 
2.33.8