1 files changed, 35 insertions, 4 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7171a957b933..feb2f42c5a07 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -751,7 +751,37 @@ out_double_mount:
         goto out;
 }
 
-static void selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
+static int selinux_cmp_sb_context(const struct super_block *oldsb,
+                                    const struct super_block *newsb)
+{
+        struct superblock_security_struct *old = oldsb->s_security;
+        struct superblock_security_struct *new = newsb->s_security;
+        char oldflags = old->flags & SE_MNTMASK;
+        char newflags = new->flags & SE_MNTMASK;
+
+        if (oldflags != newflags)
+                goto mismatch;
+        if ((oldflags & FSCONTEXT_MNT) && old->sid != new->sid)
+                goto mismatch;
+        if ((oldflags & CONTEXT_MNT) && old->mntpoint_sid != new->mntpoint_sid)
+                goto mismatch;
+        if ((oldflags & DEFCONTEXT_MNT) && old->def_sid != new->def_sid)
+                goto mismatch;
+        if (oldflags & ROOTCONTEXT_MNT) {
+                struct inode_security_struct *oldroot = oldsb->s_root->d_inode->i_security;
+                struct inode_security_struct *newroot = newsb->s_root->d_inode->i_security;
+                if (oldroot->sid != newroot->sid)
+                        goto mismatch;
+        }
+        return 0;
+mismatch:
+        printk(KERN_WARNING "SELinux: mount invalid.  Same superblock, "
+                            "different security settings for (dev %s, "
+                            "type %s)\n", newsb->s_id, newsb->s_type->name);
+        return -EBUSY;
+}
+
+static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
                                         struct super_block *newsb)
 {
         const struct superblock_security_struct *oldsbsec = oldsb->s_security;
@@ -766,14 +796,14 @@ static void selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
          * mount options.  thus we can safely deal with this superblock later
          */
         if (!ss_initialized)
-                return;
+                return 0;
 
         /* how can we clone if the old one wasn't set up?? */
         BUG_ON(!(oldsbsec->flags & SE_SBINITIALIZED));
 
-        /* if fs is reusing a sb, just let its options stand... */
+        /* if fs is reusing a sb, make sure that the contexts match */
         if (newsbsec->flags & SE_SBINITIALIZED)
-                return;
+                return selinux_cmp_sb_context(oldsb, newsb);
 
         mutex_lock(&newsbsec->lock);
 
@@ -806,6 +836,7 @@ static void selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
 
         sb_finish_set_opts(newsb);
         mutex_unlock(&newsbsec->lock);
+        return 0;
 }
 
 static int selinux_parse_opts_str(char *options,