Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6:
  DNS: Fix a NULL pointer deref when trying to read an error key [CVE-2011-1076]

Documentation/networking/dns_resolver.txt

@@ -61,7 +61,6 @@ before the more general line given above as the first match is the one taken.
 	create	dns_resolver  	foo:*	*	/usr/sbin/dns.foo %k
 
 
-
 =====
 USAGE
 =====
@@ -104,6 +103,14 @@ implemented in the module can be called after doing:
      returned also.
 
 
+===============================
+READING DNS KEYS FROM USERSPACE
+===============================
+
+Keys of dns_resolver type can be read from userspace using keyctl_read() or
+"keyctl read/print/pipe".
+
+
 =========
 MECHANISM
 =========

net/dns_resolver/dns_key.c

@@ -67,8 +67,9 @@ dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 	size_t result_len = 0;
 	const char *data = _data, *end, *opt;
 
-	kenter("%%%d,%s,'%s',%zu",
-	       key->serial, key->description, data, datalen);
+	kenter("%%%d,%s,'%*.*s',%zu",
+	       key->serial, key->description,
+	       (int)datalen, (int)datalen, data, datalen);
 
 	if (datalen <= 1 || !data || data[datalen - 1] != '\0')
 		return -EINVAL;
@@ -217,6 +218,19 @@ static void dns_resolver_describe(const struct key *key, struct seq_file *m)
 		seq_printf(m, ": %u", key->datalen);
 }
 
+/*
+ * read the DNS data
+ * - the key's semaphore is read-locked
+ */
+static long dns_resolver_read(const struct key *key,
+			      char __user *buffer, size_t buflen)
+{
+	if (key->type_data.x[0])
+		return key->type_data.x[0];
+
+	return user_read(key, buffer, buflen);
+}
+
 struct key_type key_type_dns_resolver = {
 	.name		= "dns_resolver",
 	.instantiate	= dns_resolver_instantiate,
@@ -224,7 +238,7 @@ struct key_type key_type_dns_resolver = {
 	.revoke		= user_revoke,
 	.destroy	= user_destroy,
 	.describe	= dns_resolver_describe,
-	.read		= user_read,
+	.read		= dns_resolver_read,
 };
 
 static int __init init_dns_resolver(void)