security/selinux: fix SECURITY_LSM_NATIVE_LABELS on reused superblock

commit 3815a245b50124f0865415dcb606a034e97494d4 upstream.

In the case when we're reusing a superblock, selinux_sb_clone_mnt_opts()
fails to set set_kern_flags, with the result that
nfs_clone_sb_security() incorrectly clears NFS_CAP_SECURITY_LABEL.

The result is that if you mount the same NFS filesystem twice, NFS
security labels are turned off, even if they would work fine if you
mounted the filesystem only once.

("fixes" may be not exactly the right tag, it may be more like
"fixed-other-cases-but-missed-this-one".)

Cc: Scott Mayhew <smayhew@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 0b4d3452b8b4 "security/selinux: allow security_sb_clone_mnt_opts..."
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index d6b9ed34ceae0b638ac0439adbb833a4ec1f4f32..a5d9c0146ac39d9d00ad37207de5d8be8d168530 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1000,8 +1000,11 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
        BUG_ON(!(oldsbsec->flags & SE_SBINITIALIZED));
 
        /* if fs is reusing a sb, make sure that the contexts match */
-       if (newsbsec->flags & SE_SBINITIALIZED)
+       if (newsbsec->flags & SE_SBINITIALIZED) {
+               if ((kern_flags & SECURITY_LSM_NATIVE_LABELS) && !set_context)
+                       *set_kern_flags |= SECURITY_LSM_NATIVE_LABELS;
                return selinux_cmp_sb_context(oldsb, newsb);
+       }
 
        mutex_lock(&newsbsec->lock);