datapath: Avoid pointer arithmetic on possibly-NULL pointer.

Pointer arithmetic on a null pointer yields undefined behavior, even
though it doesn't really matter in the real world (normally).

Found by Chris Eagle via Fortify.

2 files changed, 8 insertions, 2 deletions

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 338147f78..b1bcee874 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -1826,7 +1826,11 @@ static void dp_uninit_netlink(void)
 static void set_desc(void)
 {
 	const char *uuid = dmi_get_system_info(DMI_PRODUCT_UUID);
-	const char *uptr = uuid + 24;
+	const char *vendor = dmi_get_system_info(DMI_SYS_VENDOR);
+	const char *name = dmi_get_system_info(DMI_PRODUCT_NAME);
+	const char *version = dmi_get_system_info(DMI_PRODUCT_VERSION);
+	const char *serial = dmi_get_system_info(DMI_PRODUCT_SERIAL);
+	const char *uptr;
 
 	if (!uuid || *uuid == '\0' || strlen(uuid) != 36) 
 		return;
@@ -1837,6 +1841,7 @@ static void set_desc(void)
 		return;
 
 	/* Only set if the UUID is from Nicira. */
+	uptr = uuid + 24;
 	if (strncmp(uptr, NICIRA_OUI_STR, strlen(NICIRA_OUI_STR)))
 		return;
 
diff --git a/datapath/dp_dev.c b/datapath/dp_dev.c
index 7a726c39a..ec36361d6 100644
--- a/datapath/dp_dev.c
+++ b/datapath/dp_dev.c
@@ -129,7 +129,7 @@ static void
 set_uuid_mac(struct net_device *netdev)
 {
 	const char *uuid = dmi_get_system_info(DMI_PRODUCT_UUID);
-	const char *uptr = uuid + 24;
+	const char *uptr;
 	uint8_t mac[ETH_ALEN];
 	int i;
 
@@ -143,6 +143,7 @@ set_uuid_mac(struct net_device *netdev)
 
 	/* Pull out the embedded MAC address.  The kernel's sscanf doesn't
 	 * support field widths on hex digits, so we use this hack. */
+	uptr = uuid + 24;
 	for (i=0; i<ETH_ALEN; i++) {
 		unsigned char d[3];