cifs: fix IPv6 address length check

For IPv6 the userspace mount helper sends an address in the "ip="
option.  This check fails if the length is > 35 characters. I have no
idea where the magic 35 character limit came from, but it's clearly not
enough for IPv6. Fix it by making it use the INET6_ADDRSTRLEN #define.

While we're at it, use the same #define for the address length in SPNEGO
upcalls.
Reported-by: Charles R. Anderson <cra@wpi.edu>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifs_spnego.c

@@ -23,6 +23,7 @@
 #include <linux/string.h>
 #include <keys/user-type.h>
 #include <linux/key-type.h>
+#include <linux/inet.h>
 #include "cifsglob.h"
 #include "cifs_spnego.h"
 #include "cifs_debug.h"
@@ -73,9 +74,6 @@ struct key_type cifs_spnego_key_type = {
  * strlen(";sec=ntlmsspi") */
 #define MAX_MECH_STR_LEN	13
 
-/* max possible addr len eg FEDC:BA98:7654:3210:FEDC:BA98:7654:3210/128 */
-#define MAX_IPV6_ADDR_LEN	43
-
 /* strlen of "host=" */
 #define HOST_KEY_LEN		5
 
@@ -102,7 +100,7 @@ cifs_get_spnego_key(struct cifsSesInfo *sesInfo)
 	   host=hostname sec=mechanism uid=0xFF user=username */
 	desc_len = MAX_VER_STR_LEN +
 		   HOST_KEY_LEN + strlen(hostname) +
-		   IP_KEY_LEN + MAX_IPV6_ADDR_LEN +
+		   IP_KEY_LEN + INET6_ADDRSTRLEN +
 		   MAX_MECH_STR_LEN +
 		   UID_KEY_LEN + (sizeof(uid_t) * 2) +
 		   USER_KEY_LEN + strlen(sesInfo->userName) + 1;

fs/cifs/connect.c

@@ -35,6 +35,7 @@
 #include <linux/namei.h>
 #include <asm/uaccess.h>
 #include <asm/processor.h>
+#include <linux/inet.h>
 #include <net/ipv6.h>
 #include "cifspdu.h"
 #include "cifsglob.h"
@@ -960,7 +961,8 @@ cifs_parse_mount_options(char *options, const char *devname,
 		} else if (strnicmp(data, "ip", 2) == 0) {
 			if (!value || !*value) {
 				vol->UNCip = NULL;
-			} else if (strnlen(value, 35) < 35) {
+			} else if (strnlen(value, INET6_ADDRSTRLEN) <
+							INET6_ADDRSTRLEN) {
 				vol->UNCip = value;
 			} else {
 				printk(KERN_WARNING "CIFS: ip address "