FAILED: patch "[PATCH] selinux: avoid dereference of garbage after mount failure" failed to apply to 5.10-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxx>.

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 37801a36b4d68892ce807264f784d818f8d0d39b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2024040537-reexamine-stunner-cd63@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

37801a36b4d6 ("selinux: avoid dereference of garbage after mount failure")
cd2bb4cb0996 ("selinux: mark some global variables __ro_after_init")
db478cd60d55 ("selinux: make selinuxfs_mount static")

thanks,

greg k-h

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

>From 37801a36b4d68892ce807264f784d818f8d0d39b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@xxxxxxxxxxxxxx>
Date: Thu, 28 Mar 2024 20:16:58 +0100
Subject: [PATCH] selinux: avoid dereference of garbage after mount failure
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

In case kern_mount() fails and returns an error pointer return in the
error branch instead of continuing and dereferencing the error pointer.

While on it drop the never read static variable selinuxfs_mount.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 0619f0f5e36f ("selinux: wrap selinuxfs state")
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 0619a1cbbfbe..074d6c2714eb 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -2123,7 +2123,6 @@ static struct file_system_type sel_fs_type = {
 	.kill_sb	= sel_kill_sb,
 };
 
-static struct vfsmount *selinuxfs_mount __ro_after_init;
 struct path selinux_null __ro_after_init;
 
 static int __init init_sel_fs(void)
@@ -2145,18 +2144,21 @@ static int __init init_sel_fs(void)
 		return err;
 	}
 
-	selinux_null.mnt = selinuxfs_mount = kern_mount(&sel_fs_type);
-	if (IS_ERR(selinuxfs_mount)) {
+	selinux_null.mnt = kern_mount(&sel_fs_type);
+	if (IS_ERR(selinux_null.mnt)) {
 		pr_err("selinuxfs:  could not mount!\n");
-		err = PTR_ERR(selinuxfs_mount);
-		selinuxfs_mount = NULL;
+		err = PTR_ERR(selinux_null.mnt);
+		selinux_null.mnt = NULL;
+		return err;
 	}
+
 	selinux_null.dentry = d_hash_and_lookup(selinux_null.mnt->mnt_root,
 						&null_name);
 	if (IS_ERR(selinux_null.dentry)) {
 		pr_err("selinuxfs:  could not lookup null!\n");
 		err = PTR_ERR(selinux_null.dentry);
 		selinux_null.dentry = NULL;
+		return err;
 	}
 
 	return err;