auditsc: audit_krule mask accesses need bounds checking

Fixes an easy DoS and possible information disclosure.

This does nothing about the broken state of x32 auditing.

eparis: If the admin has enabled auditd and has specifically loaded
audit rules.  This bug has been around since before git.  Wow...

Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Origin: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a3c54931199565930d6d84f4c3456f6440aefd41
Backported-by: Maciej Wereski <m.wereski@partner.samsung.com>
Signed-off-by: Maciej Wereski <m.wereski@partner.samsung.com>
Change-Id: Ic36da623453b4507d93be2c68f8be6945da2df6c

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 9845cb3..03a3af8 100644 (file)
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -733,6 +733,22 @@ static enum audit_state audit_filter_task(struct task_struct *tsk, char **key)
        return AUDIT_BUILD_CONTEXT;
 }
 
+static int audit_in_mask(const struct audit_krule *rule, unsigned long val)
+{
+       int word, bit;
+
+       if (val > 0xffffffff)
+               return false;
+
+       word = AUDIT_WORD(val);
+       if (word >= AUDIT_BITMASK_SIZE)
+               return false;
+
+       bit = AUDIT_BIT(val);
+
+       return rule->mask[word] & bit;
+}
+
 /* At syscall entry and exit time, this filter is called if the
  * audit_state is not low enough that auditing cannot take place, but is
  * also not high enough that we already know we have to write an audit
@@ -750,11 +766,8 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk,
 
        rcu_read_lock();
        if (!list_empty(list)) {
-               int word = AUDIT_WORD(ctx->major);
-               int bit  = AUDIT_BIT(ctx->major);
-
                list_for_each_entry_rcu(e, list, list) {
-                       if ((e->rule.mask[word] & bit) == bit &&
+                       if (audit_in_mask(&e->rule, ctx->major) &&
                            audit_filter_rules(tsk, &e->rule, ctx, NULL,
                                               &state, false)) {
                                rcu_read_unlock();
@@ -774,20 +787,16 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk,
 static int audit_filter_inode_name(struct task_struct *tsk,
                                   struct audit_names *n,
                                   struct audit_context *ctx) {
-       int word, bit;
        int h = audit_hash_ino((u32)n->ino);
        struct list_head *list = &audit_inode_hash[h];
        struct audit_entry *e;
        enum audit_state state;
 
-       word = AUDIT_WORD(ctx->major);
-       bit  = AUDIT_BIT(ctx->major);
-
        if (list_empty(list))
                return 0;
 
        list_for_each_entry_rcu(e, list, list) {
-               if ((e->rule.mask[word] & bit) == bit &&
+               if (audit_in_mask(&e->rule, ctx->major) &&
                    audit_filter_rules(tsk, &e->rule, ctx, n, &state, false)) {
                        ctx->current_state = state;
                        return 1;