ipw2200: prevent alloc of unspecified size on stack

if log_len is larger than 4K then we are killing the stack.
allocate on heap instead and limit size to what practically can
be used (PAGE_SIZE)
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ipw2200.c

@@ -1233,9 +1233,19 @@ static ssize_t show_event_log(struct device *d,
 {
 	struct ipw_priv *priv = dev_get_drvdata(d);
 	u32 log_len = ipw_get_event_log_len(priv);
-	struct ipw_event log[log_len];
+	u32 log_size;
+	struct ipw_event *log;
 	u32 len = 0, i;
 
+	/* not using min() because of its strict type checking */
+	log_size = PAGE_SIZE / sizeof(*log) > log_len ?
+			sizeof(*log) * log_len : PAGE_SIZE;
+	log = kzalloc(log_size, GFP_KERNEL);
+	if (!log) {
+		IPW_ERROR("Unable to allocate memory for log\n");
+		return 0;
+	}
+	log_len = log_size / sizeof(*log);
 	ipw_capture_event_log(priv, log_len, log);
 
 	len += snprintf(buf + len, PAGE_SIZE - len, "%08X", log_len);
@@ -1244,6 +1254,7 @@ static ssize_t show_event_log(struct device *d,
 				"\n%08X%08X%08X",
 				log[i].time, log[i].event, log[i].data);
 	len += snprintf(buf + len, PAGE_SIZE - len, "\n");
+	kfree(log);
 	return len;
 }