5 files changed, 46 insertions, 13 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 95cdcb208dfb..6b4bf7622280 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2380,10 +2380,9 @@ int nfs_clone_sb_security(struct super_block *s, struct dentry *mntroot,
                           struct nfs_mount_info *mount_info)
 {
         /* clone any lsm security options from the parent to the new sb */
-        security_sb_clone_mnt_opts(mount_info->cloned->sb, s);
         if (mntroot->d_inode->i_op != NFS_SB(s)->nfs_client->rpc_ops->dir_inode_ops)
                 return -ESTALE;
-        return 0;
+        return security_sb_clone_mnt_opts(mount_info->cloned->sb, s);
 }
 EXPORT_SYMBOL_GPL(nfs_clone_sb_security);
 
diff --git a/include/linux/security.h b/include/linux/security.h
index eee7478cda70..4c7058dc5514 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1436,7 +1436,7 @@ struct security_operations {
                              struct path *new_path);
         int (*sb_set_mnt_opts) (struct super_block *sb,
                                 struct security_mnt_opts *opts);
-        void (*sb_clone_mnt_opts) (const struct super_block *oldsb,
+        int (*sb_clone_mnt_opts) (const struct super_block *oldsb,
                                    struct super_block *newsb);
         int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
 
@@ -1721,7 +1721,7 @@ int security_sb_mount(const char *dev_name, struct path *path,
 int security_sb_umount(struct vfsmount *mnt, int flags);
 int security_sb_pivotroot(struct path *old_path, struct path *new_path);
 int security_sb_set_mnt_opts(struct super_block *sb, struct security_mnt_opts *opts);
-void security_sb_clone_mnt_opts(const struct super_block *oldsb,
+int security_sb_clone_mnt_opts(const struct super_block *oldsb,
                                 struct super_block *newsb);
 int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
 
@@ -2011,9 +2011,11 @@ static inline int security_sb_set_mnt_opts(struct super_block *sb,
         return 0;
 }
 
-static inline void security_sb_clone_mnt_opts(const struct super_block *oldsb,
+static inline int security_sb_clone_mnt_opts(const struct super_block *oldsb,
                                               struct super_block *newsb)
-{ }
+{
+        return 0;
+}
 
 static inline int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
 {
diff --git a/security/capability.c b/security/capability.c
index 579775088967..a6290b625be9 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -98,9 +98,10 @@ static int cap_sb_set_mnt_opts(struct super_block *sb,
         return 0;
 }
 
-static void cap_sb_clone_mnt_opts(const struct super_block *oldsb,
+static int cap_sb_clone_mnt_opts(const struct super_block *oldsb,
                                   struct super_block *newsb)
 {
+        return 0;
 }
 
 static int cap_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
diff --git a/security/security.c b/security/security.c
index 7b88c6aeaed4..108281d2307a 100644
--- a/security/security.c
+++ b/security/security.c
@@ -299,10 +299,10 @@ int security_sb_set_mnt_opts(struct super_block *sb,
 }
 EXPORT_SYMBOL(security_sb_set_mnt_opts);
 
-void security_sb_clone_mnt_opts(const struct super_block *oldsb,
+int security_sb_clone_mnt_opts(const struct super_block *oldsb,
                                 struct super_block *newsb)
 {
-        security_ops->sb_clone_mnt_opts(oldsb, newsb);
+        return security_ops->sb_clone_mnt_opts(oldsb, newsb);
 }
 EXPORT_SYMBOL(security_sb_clone_mnt_opts);
 
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 2fa28c88900c..3c02be3f6732 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -750,7 +750,37 @@ 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;
@@ -765,14 +795,14 @@ 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);
 
@@ -805,6 +835,7 @@ 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,