[052/121] cifs: extend the buffer length enought for sprintf() using

[Ben Hutchings]

3.2.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Chen Gang <gang.chen@xxxxxxxxxxx>

commit 057d6332b24a4497c55a761c83c823eed9e3f23b upstream.

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@xxxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
Reviewed-by: Scott Lovenberg <scott.lovenberg@xxxxxxxxx>
Signed-off-by: Steve French <smfrench@xxxxxxxxx>
[bwh: Backported to 3.2:
 - Adjust context in sess.c
 - Drop inapplicable changes to connect.c]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -369,7 +369,7 @@ find_domain_name(struct cifs_ses *ses, c
 		if (blobptr + attrsize > blobend)
 			break;
 		if (type == NTLMSSP_AV_NB_DOMAIN_NAME) {
-			if (!attrsize)
+			if (!attrsize || attrsize >= CIFS_MAX_DOMAINNAME_LEN)
 				break;
 			if (!ses->domainName) {
 				ses->domainName =
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -38,6 +38,7 @@
 #define MAX_TREE_SIZE (2 + MAX_SERVER_SIZE + 1 + MAX_SHARE_SIZE + 1)
 #define MAX_SERVER_SIZE 15
 #define MAX_SHARE_SIZE 80
+#define CIFS_MAX_DOMAINNAME_LEN 256 /* max domain name length */
 #define MAX_USERNAME_SIZE 256	/* reasonable maximum for current servers */
 #define MAX_PASSWORD_SIZE 512	/* max for windows seems to be 256 wide chars */
 
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -198,7 +198,7 @@ static void unicode_domain_string(char *
 		bytes_ret = 0;
 	} else
 		bytes_ret = cifs_strtoUCS((__le16 *) bcc_ptr, ses->domainName,
-					  256, nls_cp);
+					  CIFS_MAX_DOMAINNAME_LEN, nls_cp);
 	bcc_ptr += 2 * bytes_ret;
 	bcc_ptr += 2;  /* account for null terminator */
 
@@ -256,8 +256,8 @@ static void ascii_ssetup_strings(char **
 
 	/* copy domain */
 	if (ses->domainName != NULL) {
-		strncpy(bcc_ptr, ses->domainName, 256);
-		bcc_ptr += strnlen(ses->domainName, 256);
+		strncpy(bcc_ptr, ses->domainName, CIFS_MAX_DOMAINNAME_LEN);
+		bcc_ptr += strnlen(ses->domainName, CIFS_MAX_DOMAINNAME_LEN);
 	} /* else we will send a null domain name
 	     so the server will default to its own domain */
 	*bcc_ptr = 0;

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