selinux: avoid dereference of garbage after mount failure

commit 37801a36b4d68892ce807264f784d818f8d0d39b upstream.

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@vger.kernel.org
Fixes: 0619f0f5e36f ("selinux: wrap selinuxfs state")
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 6fa640263216fc917635228f42536887a5b05901..2c23a5a2860860af3bad89d89db1678d8705b5bf 100644 (file)
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -2135,7 +2135,6 @@ 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)
@@ -2157,18 +2156,21 @@ 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;