1 files changed, 113 insertions, 22 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 24caaeec8894..a91c961ba38b 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -246,6 +246,7 @@ static int superblock_alloc_security(struct super_block *sb)
         sbsec->sb = sb;
         sbsec->sid = SECINITSID_UNLABELED;
         sbsec->def_sid = SECINITSID_FILE;
+        sbsec->mntpoint_sid = SECINITSID_UNLABELED;
         sb->s_security = sbsec;
 
         return 0;
@@ -319,19 +320,53 @@ enum {
         Opt_context = 1,
         Opt_fscontext = 2,
         Opt_defcontext = 4,
+        Opt_rootcontext = 8,
 };
 
 static match_table_t tokens = {
         {Opt_context, "context=%s"},
         {Opt_fscontext, "fscontext=%s"},
         {Opt_defcontext, "defcontext=%s"},
+        {Opt_rootcontext, "rootcontext=%s"},
 };
 
 #define SEL_MOUNT_FAIL_MSG "SELinux:  duplicate or incompatible mount options\n"
 
+static int may_context_mount_sb_relabel(u32 sid,
+                        struct superblock_security_struct *sbsec,
+                        struct task_security_struct *tsec)
+{
+        int rc;
+
+        rc = avc_has_perm(tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
+                          FILESYSTEM__RELABELFROM, NULL);
+        if (rc)
+                return rc;
+
+        rc = avc_has_perm(tsec->sid, sid, SECCLASS_FILESYSTEM,
+                          FILESYSTEM__RELABELTO, NULL);
+        return rc;
+}
+
+static int may_context_mount_inode_relabel(u32 sid,
+                        struct superblock_security_struct *sbsec,
+                        struct task_security_struct *tsec)
+{
+        int rc;
+        rc = avc_has_perm(tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
+                          FILESYSTEM__RELABELFROM, NULL);
+        if (rc)
+                return rc;
+
+        rc = avc_has_perm(sid, sbsec->sid, SECCLASS_FILESYSTEM,
+                          FILESYSTEM__ASSOCIATE, NULL);
+        return rc;
+}
+
 static int try_context_mount(struct super_block *sb, void *data)
 {
         char *context = NULL, *defcontext = NULL;
+        char *fscontext = NULL, *rootcontext = NULL;
         const char *name;
         u32 sid;
         int alloc = 0, rc = 0, seen = 0;
@@ -374,7 +409,7 @@ static int try_context_mount(struct super_block *sb, void *data)
 
                         switch (token) {
                         case Opt_context:
-                                if (seen) {
+                                if (seen & (Opt_context|Opt_defcontext)) {
                                         rc = -EINVAL;
                                         printk(KERN_WARNING SEL_MOUNT_FAIL_MSG);
                                         goto out_free;
@@ -390,13 +425,13 @@ static int try_context_mount(struct super_block *sb, void *data)
                                 break;
 
                         case Opt_fscontext:
-                                if (seen & (Opt_context|Opt_fscontext)) {
+                                if (seen & Opt_fscontext) {
                                         rc = -EINVAL;
                                         printk(KERN_WARNING SEL_MOUNT_FAIL_MSG);
                                         goto out_free;
                                 }
-                                context = match_strdup(&args[0]);
-                                if (!context) {
+                                fscontext = match_strdup(&args[0]);
+                                if (!fscontext) {
                                         rc = -ENOMEM;
                                         goto out_free;
                                 }
@@ -405,6 +440,22 @@ static int try_context_mount(struct super_block *sb, void *data)
                                 seen |= Opt_fscontext;
                                 break;
 
+                        case Opt_rootcontext:
+                                if (seen & Opt_rootcontext) {
+                                        rc = -EINVAL;
+                                        printk(KERN_WARNING SEL_MOUNT_FAIL_MSG);
+                                        goto out_free;
+                                }
+                                rootcontext = match_strdup(&args[0]);
+                                if (!rootcontext) {
+                                        rc = -ENOMEM;
+                                        goto out_free;
+                                }
+                                if (!alloc)
+                                        alloc = 1;
+                                seen |= Opt_rootcontext;
+                                break;
+
                         case Opt_defcontext:
                                 if (sbsec->behavior != SECURITY_FS_USE_XATTR) {
                                         rc = -EINVAL;
@@ -441,6 +492,28 @@ static int try_context_mount(struct super_block *sb, void *data)
         if (!seen)
                 goto out;
 
+        /* sets the context of the superblock for the fs being mounted. */
+        if (fscontext) {
+                rc = security_context_to_sid(fscontext, strlen(fscontext), &sid);
+                if (rc) {
+                        printk(KERN_WARNING "SELinux: security_context_to_sid"
+                               "(%s) failed for (dev %s, type %s) errno=%d\n",
+                               fscontext, sb->s_id, name, rc);
+                        goto out_free;
+                }
+
+                rc = may_context_mount_sb_relabel(sid, sbsec, tsec);
+                if (rc)
+                        goto out_free;
+
+                sbsec->sid = sid;
+        }
+
+        /*
+         * Switch to using mount point labeling behavior.
+         * sets the label used on all file below the mountpoint, and will set
+         * the superblock context if not already set.
+         */
         if (context) {
                 rc = security_context_to_sid(context, strlen(context), &sid);
                 if (rc) {
@@ -450,20 +523,38 @@ static int try_context_mount(struct super_block *sb, void *data)
                         goto out_free;
                 }
 
-                rc = avc_has_perm(tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
-                                  FILESYSTEM__RELABELFROM, NULL);
-                if (rc)
+                if (!fscontext) {
+                        rc = may_context_mount_sb_relabel(sid, sbsec, tsec);
+                        if (rc)
+                                goto out_free;
+                        sbsec->sid = sid;
+                } else {
+                        rc = may_context_mount_inode_relabel(sid, sbsec, tsec);
+                        if (rc)
+                                goto out_free;
+                }
+                sbsec->mntpoint_sid = sid;
+
+                sbsec->behavior = SECURITY_FS_USE_MNTPOINT;
+        }
+
+        if (rootcontext) {
+                struct inode *inode = sb->s_root->d_inode;
+                struct inode_security_struct *isec = inode->i_security;
+                rc = security_context_to_sid(rootcontext, strlen(rootcontext), &sid);
+                if (rc) {
+                        printk(KERN_WARNING "SELinux: security_context_to_sid"
+                               "(%s) failed for (dev %s, type %s) errno=%d\n",
+                               rootcontext, sb->s_id, name, rc);
                         goto out_free;
+                }
 
-                rc = avc_has_perm(tsec->sid, sid, SECCLASS_FILESYSTEM,
-                                  FILESYSTEM__RELABELTO, NULL);
+                rc = may_context_mount_inode_relabel(sid, sbsec, tsec);
                 if (rc)
                         goto out_free;
 
-                sbsec->sid = sid;
-
-                if (seen & Opt_context)
-                        sbsec->behavior = SECURITY_FS_USE_MNTPOINT;
+                isec->sid = sid;
+                isec->initialized = 1;
         }
 
         if (defcontext) {
@@ -478,13 +569,7 @@ static int try_context_mount(struct super_block *sb, void *data)
                 if (sid == sbsec->def_sid)
                         goto out_free;
 
-                rc = avc_has_perm(tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
-                                  FILESYSTEM__RELABELFROM, NULL);
-                if (rc)
-                        goto out_free;
-
-                rc = avc_has_perm(sid, sbsec->sid, SECCLASS_FILESYSTEM,
-                                  FILESYSTEM__ASSOCIATE, NULL);
+                rc = may_context_mount_inode_relabel(sid, sbsec, tsec);
                 if (rc)
                         goto out_free;
 
@@ -495,6 +580,8 @@ out_free:
         if (alloc) {
                 kfree(context);
                 kfree(defcontext);
+                kfree(fscontext);
+                kfree(rootcontext);
         }
 out:
         return rc;
@@ -876,8 +963,11 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
                         goto out;
                 isec->sid = sid;
                 break;
+        case SECURITY_FS_USE_MNTPOINT:
+                isec->sid = sbsec->mntpoint_sid;
+                break;
         default:
-                /* Default to the fs SID. */
+                /* Default to the fs superblock SID. */
                 isec->sid = sbsec->sid;
 
                 if (sbsec->proc) {
@@ -1843,7 +1933,8 @@ static inline int selinux_option(char *option, int len)
 {
         return (match_prefix("context=", sizeof("context=")-1, option, len) ||
                 match_prefix("fscontext=", sizeof("fscontext=")-1, option, len) ||
-                match_prefix("defcontext=", sizeof("defcontext=")-1, option, len));
+                match_prefix("defcontext=", sizeof("defcontext=")-1, option, len) ||
+                match_prefix("rootcontext=", sizeof("rootcontext=")-1, option, len));
 }
 
 static inline void take_option(char **to, char *from, int *first, int len)