[PATCH iproute2 v2] ipaddress: strengthen check on 'label' input

[Patrick Talbert <ptalbert@redhat.com>]

As mentioned in the ip-address man page, an address label must
be equal to the device name or prefixed by the device name
followed by a colon. Currently the only check on this input is
to see if the device name appears at the beginning of the label
string.

This commit adds an additional check to ensure label == dev or
continues with a colon.

Signed-off-by: Patrick Talbert <ptalbert@redhat.com>
Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
---
 ip/ipaddress.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 00da14c..fce2008 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -2040,6 +2040,22 @@ static bool ipaddr_is_multicast(inet_prefix *a)
 		return false;
 }
 
+static bool is_valid_label(const char *dev, const char *label)
+{
+	char alias[strlen(dev) + 1];
+
+	if (strlen(label) < strlen(dev))
+		return false;
+
+	strcpy(alias, dev);
+	strcat(alias, ":");
+	if (strncmp(label, dev, strlen(dev)) == 0 ||
+	    strncmp(label, alias, strlen(alias)) == 0)
+		return true;
+	else
+		return false;
+}
+
 static int ipaddr_modify(int cmd, int flags, int argc, char **argv)
 {
 	struct {
@@ -2174,8 +2190,9 @@ static int ipaddr_modify(int cmd, int flags, int argc, char **argv)
 		fprintf(stderr, "Not enough information: \"dev\" argument is required.\n");
 		return -1;
 	}
-	if (l && matches(d, l) != 0) {
-		fprintf(stderr, "\"dev\" (%s) must match \"label\" (%s).\n", d, l);
+	if (l && ! is_valid_label(d, l)) {
+		fprintf(stderr, "\"label\" (%s) must match \"dev\" (%s) or be prefixed by"
+			" \"dev\" with a colon.\n", l, d);
 		return -1;
 	}
 
-- 
1.8.3.1