iproute2: ip maddress: Check multiaddr length

ip maddress add|del takes a MAC address as argument, so insist on
getting a length of ETH_ALEN bytes. This makes sure the passed argument
is actually a MAC address and especially not an IPv4 address which
was previously accepted and silently taken as a MAC address.

While at it, do not print *argv in the error path as this has been
modified by ll_addr_a2n() and doesn't contain the full string anymore,
which can lead to misleading error messages.

Also while at it, replace the hardcoded buffer size with the actual
buffer size using sizeof().

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/ip/ipmaddr.c b/ip/ipmaddr.c
index 3400e055ad8c186a0bd85074638cbe841db8545f..d41ac63a74ecb8fd2bb5ed722211ca8164061b09 100644 (file)
--- a/ip/ipmaddr.c
+++ b/ip/ipmaddr.c
@@ -291,7 +291,7 @@ static int multiaddr_modify(int cmd, int argc, char **argv)
 {
        struct ifreq ifr = {};
        int family;
-       int fd;
+       int fd, len;
 
        if (cmd == RTM_NEWADDR)
                cmd = SIOCADDMULTI;
@@ -313,9 +313,14 @@ static int multiaddr_modify(int cmd, int argc, char **argv)
                                usage();
                        if (ifr.ifr_hwaddr.sa_data[0])
                                duparg("address", *argv);
-                       if (ll_addr_a2n(ifr.ifr_hwaddr.sa_data,
-                                       14, *argv) < 0) {
-                               fprintf(stderr, "Error: \"%s\" is not a legal ll address.\n", *argv);
+                       len = ll_addr_a2n(ifr.ifr_hwaddr.sa_data,
+                                         sizeof(ifr.ifr_hwaddr.sa_data),
+                                         *argv);
+                       if (len < 0)
+                               exit(1);
+
+                       if (len != ETH_ALEN) {
+                               fprintf(stderr, "Error: Invalid address length %d - must be %d bytes\n", len, ETH_ALEN);
                                exit(1);
                        }
                }