Smack: Add smkfstransmute mount option

Suppliment the smkfsroot mount option with another, smkfstransmute,
that does the same thing but also marks the root inode as
transmutting. This allows a freshly created filesystem to
be mounted with a transmutting heirarchy.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

2 files changed, 21 insertions, 5 deletions

diff --git a/security/smack/smack.h b/security/smack/smack.h
index 159f25bfcf45..339614c76e63 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -143,6 +143,7 @@ struct smk_port_label {
 #define SMK_FSFLOOR     "smackfsfloor="
 #define SMK_FSHAT       "smackfshat="
 #define SMK_FSROOT      "smackfsroot="
+#define SMK_FSTRANS     "smackfstransmute="
 
 #define SMACK_CIPSO_OPTION      "-CIPSO"
 
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 3669d9f9824e..6a083303501d 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -261,8 +261,9 @@ static int smack_sb_alloc_security(struct super_block *sb)
         sbsp->smk_default = smack_known_floor.smk_known;
         sbsp->smk_floor = smack_known_floor.smk_known;
         sbsp->smk_hat = smack_known_hat.smk_known;
-        sbsp->smk_initialized = 0;
-
+        /*
+         * smk_initialized will be zero from kzalloc.
+         */
         sb->s_security = sbsp;
 
         return 0;
@@ -306,6 +307,8 @@ static int smack_sb_copy_data(char *orig, char *smackopts)
                         dp = smackopts;
                 else if (strstr(cp, SMK_FSROOT) == cp)
                         dp = smackopts;
+                else if (strstr(cp, SMK_FSTRANS) == cp)
+                        dp = smackopts;
                 else
                         dp = otheropts;
 
@@ -341,8 +344,9 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
         char *op;
         char *commap;
         char *nsp;
+        int transmute = 0;
 
-        if (sp->smk_initialized != 0)
+        if (sp->smk_initialized)
                 return 0;
 
         sp->smk_initialized = 1;
@@ -373,6 +377,13 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
                         nsp = smk_import(op, 0);
                         if (nsp != NULL)
                                 sp->smk_root = nsp;
+                } else if (strncmp(op, SMK_FSTRANS, strlen(SMK_FSTRANS)) == 0) {
+                        op += strlen(SMK_FSTRANS);
+                        nsp = smk_import(op, 0);
+                        if (nsp != NULL) {
+                                sp->smk_root = nsp;
+                                transmute = 1;
+                        }
                 }
         }
 
@@ -380,11 +391,15 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
          * Initialize the root inode.
          */
         isp = inode->i_security;
-        if (isp == NULL)
+        if (inode->i_security == NULL) {
                 inode->i_security = new_inode_smack(sp->smk_root);
-        else
+                isp = inode->i_security;
+        } else
                 isp->smk_inode = sp->smk_root;
 
+        if (transmute)
+                isp->smk_flags |= SMK_INODE_TRANSMUTE;
+
         return 0;
 }