smack: deduplicate "does access rule request transmutation"

Signed-off-by: Konstantin Andreev <andreev@swemel.ru>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index fc340a6f0ddea83ada1bff2a361eb39bef0813a1..8629e58ea4fa159bd94aa7eadc2dd6cf5f6228bd 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -962,6 +962,24 @@ static int smack_inode_alloc_security(struct inode *inode)
        return 0;
 }
 
+/**
+ * smk_rule_transmutes - does access rule for (subject,object) contain 't'?
+ * @subject: a pointer to the subject's Smack label entry
+ * @object: a pointer to the object's Smack label entry
+ */
+static bool
+smk_rule_transmutes(struct smack_known *subject,
+             const struct smack_known *object)
+{
+       int may;
+
+       rcu_read_lock();
+       may = smk_access_entry(subject->smk_known, object->smk_known,
+                              &subject->smk_rules);
+       rcu_read_unlock();
+       return (may > 0) && (may & MAY_TRANSMUTE);
+}
+
 /**
  * smack_inode_init_security - copy out the smack from an inode
  * @inode: the newly created inode
@@ -977,23 +995,19 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
                                     struct xattr *xattrs, int *xattr_count)
 {
        struct task_smack *tsp = smack_cred(current_cred());
-       struct inode_smack *issp = smack_inode(inode);
-       struct smack_known *skp = smk_of_task(tsp);
-       struct smack_known *isp = smk_of_inode(inode);
+       struct inode_smack * const issp = smack_inode(inode);
        struct smack_known *dsp = smk_of_inode(dir);
        struct xattr *xattr = lsm_get_xattr_slot(xattrs, xattr_count);
-       int may;
+       bool trans_cred;
+       bool trans_rule;
 
        /*
         * If equal, transmuting already occurred in
         * smack_dentry_create_files_as(). No need to check again.
         */
-       if (tsp->smk_task != tsp->smk_transmuted) {
-               rcu_read_lock();
-               may = smk_access_entry(skp->smk_known, dsp->smk_known,
-                                      &skp->smk_rules);
-               rcu_read_unlock();
-       }
+       trans_cred = (tsp->smk_task == tsp->smk_transmuted);
+       if (!trans_cred)
+               trans_rule = smk_rule_transmutes(smk_of_task(tsp), dsp);
 
        /*
         * In addition to having smk_task equal to smk_transmuted,
@@ -1001,9 +1015,7 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
         * requests transmutation then by all means transmute.
         * Mark the inode as changed.
         */
-       if ((tsp->smk_task == tsp->smk_transmuted) ||
-           (may > 0 && ((may & MAY_TRANSMUTE) != 0) &&
-            smk_inode_transmutable(dir))) {
+       if (trans_cred || (trans_rule && smk_inode_transmutable(dir))) {
                struct xattr *xattr_transmute;
 
                /*
@@ -1012,8 +1024,8 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
                 * inode label was already set correctly in
                 * smack_inode_alloc_security().
                 */
-               if (tsp->smk_task != tsp->smk_transmuted)
-                       isp = issp->smk_inode = dsp;
+               if (!trans_cred)
+                       issp->smk_inode = dsp;
 
                issp->smk_flags |= SMK_INODE_TRANSMUTE;
                xattr_transmute = lsm_get_xattr_slot(xattrs,
@@ -1033,11 +1045,13 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
        issp->smk_flags |= SMK_INODE_INSTANT;
 
        if (xattr) {
-               xattr->value = kstrdup(isp->smk_known, GFP_NOFS);
+               const char *inode_label = issp->smk_inode->smk_known;
+
+               xattr->value = kstrdup(inode_label, GFP_NOFS);
                if (!xattr->value)
                        return -ENOMEM;
 
-               xattr->value_len = strlen(isp->smk_known);
+               xattr->value_len = strlen(inode_label);
                xattr->name = XATTR_SMACK_SUFFIX;
        }
 
@@ -4915,7 +4929,6 @@ static int smack_dentry_create_files_as(struct dentry *dentry, int mode,
        struct task_smack *otsp = smack_cred(old);
        struct task_smack *ntsp = smack_cred(new);
        struct inode_smack *isp;
-       int may;
 
        /*
         * Use the process credential unless all of
@@ -4929,18 +4942,12 @@ static int smack_dentry_create_files_as(struct dentry *dentry, int mode,
        isp = smack_inode(d_inode(dentry->d_parent));
 
        if (isp->smk_flags & SMK_INODE_TRANSMUTE) {
-               rcu_read_lock();
-               may = smk_access_entry(otsp->smk_task->smk_known,
-                                      isp->smk_inode->smk_known,
-                                      &otsp->smk_task->smk_rules);
-               rcu_read_unlock();
-
                /*
                 * If the directory is transmuting and the rule
                 * providing access is transmuting use the containing
                 * directory label instead of the process label.
                 */
-               if (may > 0 && (may & MAY_TRANSMUTE)) {
+               if (smk_rule_transmutes(otsp->smk_task, isp->smk_inode)) {
                        ntsp->smk_task = isp->smk_inode;
                        ntsp->smk_transmuted = ntsp->smk_task;
                }