1 files changed, 46 insertions, 185 deletions

diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index 853a968e82d..0eb87026cad 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -4,6 +4,8 @@
  *   Copyright (c) 2007 Igor Mammedov
  *   Author(s): Igor Mammedov (niallain@gmail.com)
  *              Steve French (sfrench@us.ibm.com)
+ *              Wang Lei (wang840925@gmail.com)
+ *		David Howells (dhowells@redhat.com)
  *
  *   Contains the CIFS DFS upcall routines used for hostname to
  *   IP address translation.
@@ -24,214 +26,73 @@
  */
 
 #include <linux/slab.h>
-#include <linux/keyctl.h>
-#include <linux/key-type.h>
-#include <keys/user-type.h>
+#include <linux/dns_resolver.h>
 #include "dns_resolve.h"
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
 
-static const struct cred *dns_resolver_cache;
-
-/* Checks if supplied name is IP address
- * returns:
- * 		1 - name is IP
- * 		0 - name is not IP
- */
-static int
-is_ip(char *name)
-{
-	struct sockaddr_storage ss;
-
-	return cifs_convert_address(name, &ss);
-}
-
-static int
-dns_resolver_instantiate(struct key *key, const void *data,
-		size_t datalen)
-{
-	int rc = 0;
-	char *ip;
-
-	ip = kmalloc(datalen + 1, GFP_KERNEL);
-	if (!ip)
-		return -ENOMEM;
-
-	memcpy(ip, data, datalen);
-	ip[datalen] = '\0';
-
-	/* make sure this looks like an address */
-	if (!is_ip(ip)) {
-		kfree(ip);
-		return -EINVAL;
-	}
-
-	key->type_data.x[0] = datalen;
-	key->payload.data = ip;
-
-	return rc;
-}
-
-static void
-dns_resolver_destroy(struct key *key)
-{
-	kfree(key->payload.data);
-}
-
-struct key_type key_type_dns_resolver = {
-	.name        = "dns_resolver",
-	.def_datalen = sizeof(struct in_addr),
-	.describe    = user_describe,
-	.instantiate = dns_resolver_instantiate,
-	.destroy     = dns_resolver_destroy,
-	.match       = user_match,
-};
-
-/* Resolves server name to ip address.
- * input:
- * 	unc - server UNC
- * output:
- * 	*ip_addr - pointer to server ip, caller responcible for freeing it.
- * return 0 on success
+/**
+ * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
+ * @unc: UNC path specifying the server
+ * @ip_addr: Where to return the IP address.
+ *
+ * The IP address will be returned in string form, and the caller is
+ * responsible for freeing it.
+ *
+ * Returns length of result on success, -ve on error.
  */
 int
 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 {
-	const struct cred *saved_cred;
-	int rc = -EAGAIN;
-	struct key *rkey = ERR_PTR(-EAGAIN);
+	struct sockaddr_storage ss;
+	const char *hostname, *sep;
 	char *name;
-	char *data = NULL;
-	int len;
+	int len, rc;
 
 	if (!ip_addr || !unc)
 		return -EINVAL;
 
-	/* search for server name delimiter */
 	len = strlen(unc);
 	if (len < 3) {
 		cFYI(1, "%s: unc is too short: %s", __func__, unc);
 		return -EINVAL;
 	}
-	len -= 2;
-	name = memchr(unc+2, '\\', len);
-	if (!name) {
-		cFYI(1, "%s: probably server name is whole unc: %s",
-					__func__, unc);
-	} else {
-		len = (name - unc) - 2/* leading // */;
-	}
-
-	name = kmalloc(len+1, GFP_KERNEL);
-	if (!name) {
-		rc = -ENOMEM;
-		return rc;
-	}
-	memcpy(name, unc+2, len);
-	name[len] = 0;
-
-	if (is_ip(name)) {
-		cFYI(1, "%s: it is IP, skipping dns upcall: %s",
-					__func__, name);
-		data = name;
-		goto skip_upcall;
-	}
 
-	saved_cred = override_creds(dns_resolver_cache);
-	rkey = request_key(&key_type_dns_resolver, name, "");
-	revert_creds(saved_cred);
-	if (!IS_ERR(rkey)) {
-		if (!(rkey->perm & KEY_USR_VIEW)) {
-			down_read(&rkey->sem);
-			rkey->perm |= KEY_USR_VIEW;
-			up_read(&rkey->sem);
-		}
-		len = rkey->type_data.x[0];
-		data = rkey->payload.data;
-	} else {
-		cERROR(1, "%s: unable to resolve: %s", __func__, name);
-		goto out;
-	}
-
-skip_upcall:
-	if (data) {
-		*ip_addr = kmalloc(len + 1, GFP_KERNEL);
-		if (*ip_addr) {
-			memcpy(*ip_addr, data, len + 1);
-			if (!IS_ERR(rkey))
-				cFYI(1, "%s: resolved: %s to %s", __func__,
-							name,
-							*ip_addr
-					);
-			rc = 0;
-		} else {
-			rc = -ENOMEM;
-		}
-		if (!IS_ERR(rkey))
-			key_put(rkey);
-	}
+	/* Discount leading slashes for cifs */
+	len -= 2;
+	hostname = unc + 2;
 
-out:
-	kfree(name);
+	/* Search for server name delimiter */
+	sep = memchr(hostname, '\\', len);
+	if (sep)
+		len = sep - unc;
+	else
+		cFYI(1, "%s: probably server name is whole unc: %s",
+		     __func__, unc);
+
+	/* Try to interpret hostname as an IPv4 or IPv6 address */
+	rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
+	if (rc > 0)
+		goto name_is_IP_address;
+
+	/* Perform the upcall */
+	rc = dns_query(NULL, hostname, len, NULL, ip_addr, NULL);
+	if (rc < 0)
+		cERROR(1, "%s: unable to resolve: %*.*s",
+		       __func__, len, len, hostname);
+	else
+		cFYI(1, "%s: resolved: %*.*s to %s",
+		     __func__, len, len, hostname, *ip_addr);
 	return rc;
-}
 
-int __init cifs_init_dns_resolver(void)
-{
-	struct cred *cred;
-	struct key *keyring;
-	int ret;
-
-	printk(KERN_NOTICE "Registering the %s key type\n",
-	       key_type_dns_resolver.name);
-
-	/* create an override credential set with a special thread keyring in
-	 * which DNS requests are cached
-	 *
-	 * this is used to prevent malicious redirections from being installed
-	 * with add_key().
-	 */
-	cred = prepare_kernel_cred(NULL);
-	if (!cred)
+name_is_IP_address:
+	name = kmalloc(len + 1, GFP_KERNEL);
+	if (!name)
 		return -ENOMEM;
-
-	keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
-			    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
-			    KEY_USR_VIEW | KEY_USR_READ,
-			    KEY_ALLOC_NOT_IN_QUOTA);
-	if (IS_ERR(keyring)) {
-		ret = PTR_ERR(keyring);
-		goto failed_put_cred;
-	}
-
-	ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
-	if (ret < 0)
-		goto failed_put_key;
-
-	ret = register_key_type(&key_type_dns_resolver);
-	if (ret < 0)
-		goto failed_put_key;
-
-	/* instruct request_key() to use this special keyring as a cache for
-	 * the results it looks up */
-	cred->thread_keyring = keyring;
-	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
-	dns_resolver_cache = cred;
+	memcpy(name, hostname, len);
+	name[len] = 0;
+	cFYI(1, "%s: unc is IP, skipping dns upcall: %s", __func__, name);
+	*ip_addr = name;
 	return 0;
-
-failed_put_key:
-	key_put(keyring);
-failed_put_cred:
-	put_cred(cred);
-	return ret;
-}
-
-void cifs_exit_dns_resolver(void)
-{
-	key_revoke(dns_resolver_cache->thread_keyring);
-	unregister_key_type(&key_type_dns_resolver);
-	put_cred(dns_resolver_cache);
-	printk(KERN_NOTICE "Unregistered %s key type\n",
-	       key_type_dns_resolver.name);
 }