[PATCH v2] cifs: extend the buffer length enought for sprintf() using

[Chen Gang <gang.chen-bOixZGp5f+dBDgjK7y7TUQ@public.gmane.org>]

For cifs_set_cifscreds() in "fs/cifs/connect.c", 'desc' buffer length
is 'CIFSCREDS_DESC_SIZE' (56 is less than 256), and 'ses->domainName'
length may be "255 + '\0'".

The related sprintf() may cause memory overflow, so need extend related
buffer enough to hold all things.

It is also necessary to be sure of 'ses->domainName' must be less than
256, and define the related macro instead of hard code number '256'.

Signed-off-by: Chen Gang <gang.chen-bOixZGp5f+dBDgjK7y7TUQ@public.gmane.org>
---
 fs/cifs/cifsencrypt.c |    2 +-
 fs/cifs/cifsglob.h    |    1 +
 fs/cifs/connect.c     |    7 ++++---
 fs/cifs/sess.c        |    6 +++---
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index 45e57cc..bb84d7c 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -421,7 +421,7 @@ find_domain_name(struct cifs_ses *ses, const struct nls_table *nls_cp)
 		if (blobptr + attrsize > blobend)
 			break;
 		if (type == NTLMSSP_AV_NB_DOMAIN_NAME) {
-			if (!attrsize)
+			if (!attrsize || attrsize >= MAX_DOMAINNAME_SIZE)
 				break;
 			if (!ses->domainName) {
 				ses->domainName =
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 33f17ed..64bb4c5 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -44,6 +44,7 @@
 #define MAX_TREE_SIZE (2 + MAX_SERVER_SIZE + 1 + MAX_SHARE_SIZE + 1)
 #define MAX_SERVER_SIZE 15
 #define MAX_SHARE_SIZE 80
+#define MAX_DOMAINNAME_SIZE 256	/* maximum fully qualified domain name (FQDN) */
 #define MAX_USERNAME_SIZE 256	/* reasonable maximum for current servers */
 #define MAX_PASSWORD_SIZE 512	/* max for windows seems to be 256 wide chars */
 
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index fa68813..3f9dcf7 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1675,7 +1675,8 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			if (string == NULL)
 				goto out_nomem;
 
-			if (strnlen(string, 256) == 256) {
+			if (strnlen(string, MAX_DOMAINNAME_SIZE)
+					== MAX_DOMAINNAME_SIZE) {
 				printk(KERN_WARNING "CIFS: domain name too"
 						    " long\n");
 				goto cifs_parse_mount_err;
@@ -2276,8 +2277,8 @@ cifs_put_smb_ses(struct cifs_ses *ses)
 
 #ifdef CONFIG_KEYS
 
-/* strlen("cifs:a:") + INET6_ADDRSTRLEN + 1 */
-#define CIFSCREDS_DESC_SIZE (7 + INET6_ADDRSTRLEN + 1)
+/* strlen("cifs:a:") + MAX_DOMAINNAME_SIZE + 1 */
+#define CIFSCREDS_DESC_SIZE (7 + MAX_DOMAINNAME_SIZE + 1)
 
 /* Populate username and pw fields from keyring if possible */
 static int
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 79358e3..57b1537 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -197,7 +197,7 @@ static void unicode_domain_string(char **pbcc_area, struct cifs_ses *ses,
 		bytes_ret = 0;
 	} else
 		bytes_ret = cifs_strtoUTF16((__le16 *) bcc_ptr, ses->domainName,
-					    256, nls_cp);
+					    MAX_DOMAINNAME_SIZE, nls_cp);
 	bcc_ptr += 2 * bytes_ret;
 	bcc_ptr += 2;  /* account for null terminator */
 
@@ -255,8 +255,8 @@ static void ascii_ssetup_strings(char **pbcc_area, struct cifs_ses *ses,
 
 	/* copy domain */
 	if (ses->domainName != NULL) {
-		strncpy(bcc_ptr, ses->domainName, 256);
-		bcc_ptr += strnlen(ses->domainName, 256);
+		strncpy(bcc_ptr, ses->domainName, MAX_DOMAINNAME_SIZE);
+		bcc_ptr += strnlen(ses->domainName, MAX_DOMAINNAME_SIZE);
 	} /* else we will send a null domain name
 	     so the server will default to its own domain */
 	*bcc_ptr = 0;
-- 
1.7.7.6