cifs: fix a possible null pointer deref in decode_ascii_ssetup

When kzalloc fails, we will end up doing NULL pointer derefrence
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/sess.c

@@ -243,10 +243,11 @@ static void decode_ascii_ssetup(char **pbcc_area, __u16 bleft,
 	kfree(ses->serverOS);
 
 	ses->serverOS = kzalloc(len + 1, GFP_KERNEL);
-	if (ses->serverOS)
+	if (ses->serverOS) {
 		strncpy(ses->serverOS, bcc_ptr, len);
-	if (strncmp(ses->serverOS, "OS/2", 4) == 0)
-		cifs_dbg(FYI, "OS/2 server\n");
+		if (strncmp(ses->serverOS, "OS/2", 4) == 0)
+			cifs_dbg(FYI, "OS/2 server\n");
+	}
 
 	bcc_ptr += len + 1;
 	bleft -= len + 1;