AUDIT: Prevent duplicate syscall rules

The following patch against audit.81 prevents duplicate syscall rules in
a given filter list by walking the list on each rule add.

I also removed the unused struct audit_entry in audit.c and made the
static inlines in auditsc.c consistent.

Signed-off-by: Amy Griffis <amy.griffis@hp.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 56 insertions, 44 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index d321e251d32b..8376ec10cf24 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -142,11 +142,6 @@ static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
         nlh->nlmsg_pid = pid;
 }
 
-struct audit_entry {
-        struct list_head  list;
-        struct audit_rule rule;
-};
-
 static void audit_panic(const char *message)
 {
         switch (audit_failure)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 818ef9fdab3c..488ba3dea8bb 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -190,9 +190,36 @@ struct audit_entry {
 
 extern int audit_pid;
 
+/* Copy rule from user-space to kernel-space.  Called from 
+ * audit_add_rule during AUDIT_ADD. */
+static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
+{
+        int i;
+
+        if (s->action != AUDIT_NEVER
+            && s->action != AUDIT_POSSIBLE
+            && s->action != AUDIT_ALWAYS)
+                return -1;
+        if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
+                return -1;
+        if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
+                return -1;
+
+        d->flags        = s->flags;
+        d->action       = s->action;
+        d->field_count  = s->field_count;
+        for (i = 0; i < d->field_count; i++) {
+                d->fields[i] = s->fields[i];
+                d->values[i] = s->values[i];
+        }
+        for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i];
+        return 0;
+}
+
 /* Check to see if two rules are identical.  It is called from
+ * audit_add_rule during AUDIT_ADD and 
  * audit_del_rule during AUDIT_DEL. */
-static int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
+static inline int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
 {
         int i;
 
@@ -221,18 +248,37 @@ static int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
 /* Note that audit_add_rule and audit_del_rule are called via
  * audit_receive() in audit.c, and are protected by
  * audit_netlink_sem. */
-static inline void audit_add_rule(struct audit_entry *entry,
+static inline int audit_add_rule(struct audit_rule *rule,
                                   struct list_head *list)
 {
+        struct audit_entry  *entry;
+
+        /* Do not use the _rcu iterator here, since this is the only
+         * addition routine. */
+        list_for_each_entry(entry, list, list) {
+                if (!audit_compare_rule(rule, &entry->rule)) {
+                        return -EEXIST;
+                }
+        }
+
+        if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL)))
+                return -ENOMEM;
+        if (audit_copy_rule(&entry->rule, rule)) {
+                kfree(entry);
+                return -EINVAL;
+        }
+
         if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
                 entry->rule.flags &= ~AUDIT_FILTER_PREPEND;
                 list_add_rcu(&entry->list, list);
         } else {
                 list_add_tail_rcu(&entry->list, list);
         }
+
+        return 0;
 }
 
-static void audit_free_rule(struct rcu_head *head)
+static inline void audit_free_rule(struct rcu_head *head)
 {
         struct audit_entry *e = container_of(head, struct audit_entry, rcu);
         kfree(e);
@@ -258,32 +304,6 @@ static inline int audit_del_rule(struct audit_rule *rule,
         return -ENOENT;         /* No matching rule */
 }
 
-/* Copy rule from user-space to kernel-space.  Called during
- * AUDIT_ADD. */
-static int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
-{
-        int i;
-
-        if (s->action != AUDIT_NEVER
-            && s->action != AUDIT_POSSIBLE
-            && s->action != AUDIT_ALWAYS)
-                return -1;
-        if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
-                return -1;
-        if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
-                return -1;
-
-        d->flags        = s->flags;
-        d->action       = s->action;
-        d->field_count  = s->field_count;
-        for (i = 0; i < d->field_count; i++) {
-                d->fields[i] = s->fields[i];
-                d->values[i] = s->values[i];
-        }
-        for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i];
-        return 0;
-}
-
 static int audit_list_rules(void *_dest)
 {
         int pid, seq;
@@ -313,7 +333,6 @@ static int audit_list_rules(void *_dest)
 int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
                                                         uid_t loginuid)
 {
-        struct audit_entry *entry;
         struct task_struct *tsk;
         int *dest;
         int                err = 0;
@@ -340,16 +359,14 @@ int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
                 }
                 break;
         case AUDIT_ADD:
-                if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL)))
-                        return -ENOMEM;
-                if (audit_copy_rule(&entry->rule, data)) {
-                        kfree(entry);
+                listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
+                if (listnr >= AUDIT_NR_FILTERS)
                         return -EINVAL;
-                }
-                listnr = entry->rule.flags & ~AUDIT_FILTER_PREPEND;
-                audit_add_rule(entry, &audit_filter_list[listnr]);
-                audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, 
-                                "auid=%u added an audit rule\n", loginuid);
+
+                err = audit_add_rule(data, &audit_filter_list[listnr]);
+                if (!err)
+                        audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
+                                  "auid=%u added an audit rule\n", loginuid);
                 break;
         case AUDIT_DEL:
                 listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;