From: Ben Hutchings <ben@decadent.org.uk>
Date: Fri, 25 Sep 2015 20:28:10 +0100
Subject: tools/hv: Fix fortify format warning
Forwarded: no

With fortify enabled, gcc warns:

tools/hv/hv_kvp_daemon.c:705:2: error: format not a string literal and no format arguments [-Werror=format-security]
  snprintf(dev_id, sizeof(dev_id), kvp_net_dir);
  ^

kvp_net_dir is a pointer to a string literal, but lacks const
qualification.  As it is never modified, it should be a const
array rather than a pointer.

Also, while snprintf() has a bounds check, the following strcat()s
do not.  Combine them into a single snprintf().

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/tools/hv/hv_kvp_daemon.c
+++ b/tools/hv/hv_kvp_daemon.c
@@ -691,10 +691,10 @@ static char *kvp_mac_to_if_name(char *ma
 	DIR *dir;
 	struct dirent *entry;
 	FILE    *file;
-	char    *p, *q, *x;
+	char    *p, *x;
 	char    *if_name = NULL;
 	char    buf[256];
-	char *kvp_net_dir = "/sys/class/net/";
+	const char kvp_net_dir[] = "/sys/class/net/";
 	char dev_id[256];
 	unsigned int i;
 
@@ -702,17 +702,9 @@ static char *kvp_mac_to_if_name(char *ma
 	if (dir == NULL)
 		return NULL;
 
-	snprintf(dev_id, sizeof(dev_id), kvp_net_dir);
-	q = dev_id + strlen(kvp_net_dir);
-
 	while ((entry = readdir(dir)) != NULL) {
-		/*
-		 * Set the state for the next pass.
-		 */
-		*q = '\0';
-
-		strcat(dev_id, entry->d_name);
-		strcat(dev_id, "/address");
+		snprintf(dev_id, sizeof(dev_id), "%s%s/address",
+			 kvp_net_dir, entry->d_name);
 
 		file = fopen(dev_id, "r");
 		if (file == NULL)