FAILED: patch "[PATCH] f2fs: prevent creating duplicate encrypted filenames" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-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 bfc2b7e8518999003a61f91c1deb5e88ed77b07d Mon Sep 17 00:00:00 2001
From: Eric Biggers <[email protected]>
Date: Tue, 17 Nov 2020 23:56:07 -0800
Subject: [PATCH] f2fs: prevent creating duplicate encrypted filenames

As described in "fscrypt: add fscrypt_is_nokey_name()", it's possible to create a duplicate filename in an encrypted directory by creating a file concurrently with adding the directory's encryption key.

Fix this bug on f2fs by rejecting no-key dentries in f2fs_add_link().

Note that the weird check for the current task in f2fs_do_add_link() seems to make this bug difficult to reproduce on f2fs.

index cb700d797296..9a321c52face 100644
@@ -3251,6 +3251,8 @@ bool f2fs_empty_dir(struct inode *dir);
 
 static inline int f2fs_add_link(struct dentry *dentry, struct inode *inode)
 {
+	if (fscrypt_is_nokey_name(dentry))
+		return -ENOKEY;
 	return f2fs_do_add_link(d_inode(dentry->d_parent), &dentry->d_name,
 				inode, inode->i_ino, inode->i_mode);
 }

Oops, got these out of order, my fault, let me try this again...

Ok, got it applied to 5.10.y, but nothing else due to the dependant patch not working anywhere other than that :(

thanks,

greg k-h