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-rw-r--r--fs/cifs/dns_resolve.c229
1 files changed, 46 insertions, 183 deletions
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index aa967e7917f8..0eb87026cad3 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.
@@ -24,212 +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(const char *name, int len)
-{
- struct sockaddr_storage ss;
-
- return cifs_convert_address((struct sockaddr *)&ss, name, len);
-}
-
-static int
-dns_resolver_instantiate(struct key *key, const void *data,
- size_t datalen)
-{
- int rc = 0;
- char *ip;
-
- /* make sure this looks like an address */
- if (!is_ip(data, datalen))
- return -EINVAL;
-
- ip = kmalloc(datalen + 1, GFP_KERNEL);
- if (!ip)
- return -ENOMEM;
-
- memcpy(ip, data, datalen);
- ip[datalen] = '\0';
-
- 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 the length of the returned string 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, len)) {
- 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 = len;
- } 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);
}

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