Merge tag 'selinux-pr-20230914' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

Pull selinux fix from Paul Moore:
 "A relatively small SELinux patch to fix an issue with a
  vfs/LSM/SELinux patch that went upstream during the recent merge
  window.

  The short version is that the original patch changed how we
  initialized mount options to resolve a NFS issue and we inadvertently
  broke a use case due to the changed behavior.

  The fix restores this behavior for the cases that require it while
  keeping the original NFS fix in place"

* tag 'selinux-pr-20230914' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: fix handling of empty opts in selinux_fs_context_submount()

Author: torvalds

security/selinux/hooks.c

@@ -2775,14 +2775,20 @@ static int selinux_umount(struct vfsmount *mnt, int flags)
 static int selinux_fs_context_submount(struct fs_context *fc,
 				   struct super_block *reference)
 {
-	const struct superblock_security_struct *sbsec;
+	const struct superblock_security_struct *sbsec = selinux_superblock(reference);
 	struct selinux_mnt_opts *opts;
 
+	/*
+	 * Ensure that fc->security remains NULL when no options are set
+	 * as expected by selinux_set_mnt_opts().
+	 */
+	if (!(sbsec->flags & (FSCONTEXT_MNT|CONTEXT_MNT|DEFCONTEXT_MNT)))
+		return 0;
+
 	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
 	if (!opts)
 		return -ENOMEM;
 
-	sbsec = selinux_superblock(reference);
 	if (sbsec->flags & FSCONTEXT_MNT)
 		opts->fscontext_sid = sbsec->sid;
 	if (sbsec->flags & CONTEXT_MNT)