[Trusty][CVE-2014-3917] (upstream) auditsc: audit_krule mask accesses need bounds checking

[Rafael David Tinoco]

From 99424193549932e0b54a41c349a1aabbe85160be Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto at amacapital.net>
Date: Wed, 28 May 2014 23:09:58 -0400
Subject: auditsc: audit_krule mask accesses need bounds checking

CVE-2014-3917

BugLink: http://bugs.launchpad.net/bugs/1302605

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...

OriginalAuthor: Andy Lutomirski <luto at amacapital.net>
Signed-off-by: Andy Lutomirski <luto at amacapital.net>
(cherry-picked from commit a3c54931199565930d6d84f4c3456f6440aefd41 v3.16-rc6)
Signed-off-by: Eric Paris <eparis at redhat.com>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Rafael David Tinoco <rafael.tinoco at canonical.com>
---
 kernel/auditsc.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b590eae..d36a620 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -720,6 +720,22 @@ 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
@@ -737,11 +753,8 @@ 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();
@@ -761,20 +774,16 @@ 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;
-- 
1.9.1
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