pppoe: Fail if ethernet interface name is too long

If the name of the ethernet interface is longer than can fit in the
relevant structure used for system calls, generate an error rather
than using a truncated interface name.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/pppd/plugins/pppoe/if.c b/pppd/plugins/pppoe/if.c
index 4b13ecc19866eed617fa8ce038d8b2b728ceeba2..d5a4624fce5fe829d61d035847d373bfc94cc4f9 100644 (file)
--- a/pppd/plugins/pppoe/if.c
+++ b/pppd/plugins/pppoe/if.c
@@ -99,6 +99,7 @@ openInterface(char const *ifname, UINT16_t type, unsigned char *hwaddr)
     int fd;
     struct ifreq ifr;
     int domain, stype;
+    size_t maxlen;
 
 #ifdef HAVE_STRUCT_SOCKADDR_LL
     struct sockaddr_ll sa;
@@ -111,11 +112,18 @@ openInterface(char const *ifname, UINT16_t type, unsigned char *hwaddr)
 #ifdef HAVE_STRUCT_SOCKADDR_LL
     domain = PF_PACKET;
     stype = SOCK_RAW;
+    maxlen = IFNAMSIZ;
 #else
     domain = PF_INET;
     stype = SOCK_PACKET;
+    maxlen = sizeof(sa.sa_data);
 #endif
 
+    if (strlen(ifname) >= maxlen) {
+       error("Can't use interface %.16s: name is too long", ifname);
+       return -1;
+    }
+
     if ((fd = socket(domain, stype, htons(type))) < 0) {
        /* Give a more helpful message for the common error case */
        if (errno == EPERM) {