s390/hvc_iucv: add simple wildcard matches to the iucv allow filter

Introduce a wildcard character to filter a range of z/VM user IDs with a single
filter entry. Only the leading portion up to the wildcard of an filter entry
contributes to the match.

This reduces the filter size and avoids configuration updates when deploying
new terminal server instances.

Signed-off-by: Hendrik Brueckner <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/tty/hvc/hvc_iucv.c

···
 /*
- * hvc_iucv.c - z/VM IUCV hypervisor console (HVC) device driver
+ * z/VM IUCV hypervisor console (HVC) device driver
  *
  * This HVC device driver provides terminal access using
  * z/VM IUCV communication paths.
  *
- * Copyright IBM Corp. 2008, 2009
+ * Copyright IBM Corp. 2008, 2013
  *
  * Author(s):	Hendrik Brueckner <[e-mail]>
  */
···
 #define IUCV_HVC_CON_IDX	(0)
 /* List of z/VM user ID filter entries (struct iucv_vmid_filter) */
 #define MAX_VMID_FILTER		(500)
+#define FILTER_WILDCARD_CHAR	'*'
 static size_t hvc_iucv_filter_size;
 static void *hvc_iucv_filter;
 static const char *hvc_iucv_filter_string;
···
  * hvc_iucv_filter_connreq() - Filter connection request based on z/VM user ID
  * @ipvmid:	Originating z/VM user ID (right padded with blanks)
  *
- * Returns 0 if the z/VM user ID @ipvmid is allowed to connection, otherwise
- * non-zero.
+ * Returns 0 if the z/VM user ID that is specified with @ipvmid is permitted to
+ * connect, otherwise non-zero.
  */
 static int hvc_iucv_filter_connreq(u8 ipvmid[8])
 {
-	size_t i;
+	const char *wildcard, *filter_entry;
+	size_t i, len;
 
 	/* Note: default policy is ACCEPT if no filter is set */
 	if (!hvc_iucv_filter_size)
 		return 0;
 
-	for (i = 0; i < hvc_iucv_filter_size; i++)
-		if (0 == memcmp(ipvmid, hvc_iucv_filter + (8 * i), 8))
+	for (i = 0; i < hvc_iucv_filter_size; i++) {
+		filter_entry = hvc_iucv_filter + (8 * i);
+
+		/* If a filter entry contains the filter wildcard character,
+		 * reduce the length to match the leading portion of the user
+		 * ID only (wildcard match).  Characters following the wildcard
+		 * are ignored.
+		 */
+		wildcard = strnchr(filter_entry, 8, FILTER_WILDCARD_CHAR);
+		len = (wildcard) ? wildcard - filter_entry : 8;
+		if (0 == memcmp(ipvmid, filter_entry, len))
 			return 0;
+	}
 	return 1;
 }
 
···
 /**
  * hvc_iucv_parse_filter() - Parse filter for a single z/VM user ID
  * @filter:	String containing a comma-separated list of z/VM user IDs
+ * @dest:	Location where to store the parsed z/VM user ID
  */
 static const char *hvc_iucv_parse_filter(const char *filter, char *dest)
 {
···
 	/* check for '\n' (if called from sysfs) */
 	if (filter[len - 1] == '\n')
 		len--;
+
+	/* prohibit filter entries containing the wildcard character only */
+	if (len == 1 && *filter == FILTER_WILDCARD_CHAR)
+		return ERR_PTR(-EINVAL);
 
 	if (len > 8)
 		return ERR_PTR(-EINVAL);