FAILED: patch "[PATCH] fscrypt: destroy keyring after security_sb_delete()" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.10-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 <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x ccb820dc7d2236b1af0d54ae038a27b5b6d5ae5a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '168000451363159@kroah.com' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

ccb820dc7d22 ("fscrypt: destroy keyring after security_sb_delete()")
83e804f0bfee ("fs,security: Add sb_delete hook")

thanks,

greg k-h

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

From ccb820dc7d2236b1af0d54ae038a27b5b6d5ae5a Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Mon, 13 Mar 2023 15:12:29 -0700
Subject: [PATCH] fscrypt: destroy keyring after security_sb_delete()

fscrypt_destroy_keyring() must be called after all potentially-encrypted
inodes were evicted; otherwise it cannot safely destroy the keyring.
Since inodes that are in-use by the Landlock LSM don't get evicted until
security_sb_delete(), this means that fscrypt_destroy_keyring() must be
called *after* security_sb_delete().

This fixes a WARN_ON followed by a NULL dereference, only possible if
Landlock was being used on encrypted files.

Fixes: d7e7b9af104c ("fscrypt: stop using keyrings subsystem for fscrypt_master_key")
Cc: stable@vger.kernel.org
Reported-by: syzbot+93e495f6a4f748827c88@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/00000000000044651705f6ca1e30@google.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230313221231.272498-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/fs/super.c b/fs/super.c
index 84332d5cb817..04bc62ab7dfe 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -475,13 +475,22 @@ void generic_shutdown_super(struct super_block *sb)
 
 		cgroup_writeback_umount();
 
-		/* evict all inodes with zero refcount */
+		/* Evict all inodes with zero refcount. */
 		evict_inodes(sb);
-		/* only nonzero refcount inodes can have marks */
+
+		/*
+		 * Clean up and evict any inodes that still have references due
+		 * to fsnotify or the security policy.
+		 */
 		fsnotify_sb_delete(sb);
-		fscrypt_destroy_keyring(sb);
 		security_sb_delete(sb);
 
+		/*
+		 * Now that all potentially-encrypted inodes have been evicted,
+		 * the fscrypt keyring can be destroyed.
+		 */
+		fscrypt_destroy_keyring(sb);
+
 		if (sb->s_dio_done_wq) {
 			destroy_workqueue(sb->s_dio_done_wq);
 			sb->s_dio_done_wq = NULL;