FAILED: patch "[PATCH] NFSv4: Handle case where the lookup of a directory fails" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ac795161c93699d600db16c1a8cc23a65a1eceaf Mon Sep 17 00:00:00 2001
From: Trond Myklebust <[email protected]>
Date: Thu, 6 Jan 2022 18:24:02 -0500
Subject: [PATCH] NFSv4: Handle case where the lookup of a directory fails

If the application sets the O_DIRECTORY flag, and tries to open a regular file, nfs_atomic_open() will punt to doing a regular lookup. If the server then returns a regular file, we will happily return a file descriptor with uninitialised open state.

The fix is to return the expected ENOTDIR error in these cases.

index 2884138848f4..408c3bb549b1 100644
@@ -1994,6 +1994,19 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
 
 no_open:
 	res = nfs_lookup(dir, dentry, lookup_flags);
+	if (!res) {
+		inode = d_inode(dentry);
+		if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
+		    !S_ISDIR(inode->i_mode))
+			res = ERR_PTR(-ENOTDIR);
+	} else if (!IS_ERR(res)) {
+		inode = d_inode(res);
+		if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
+		    !S_ISDIR(inode->i_mode)) {
+			dput(res);
+			res = ERR_PTR(-ENOTDIR);
+		}
+	}
 	if (switched) {
 		d_lookup_done(dentry);
 		if (!res)