Don't try to allocate more than WTAP_MAX_PACKET_SIZE. Fixes a crash

reported in bug 3849.

svn path=/trunk/; revision=29364

wiretap/erf.c

@@ -218,6 +218,13 @@ extern int erf_open(wtap *wth, int *err, gchar **err_info _U_)
 
     /* The file_seek function do not return an error if the end of file
        is reached whereas the record is truncated */
+    if (packet_size > WTAP_MAX_PACKET_SIZE) {
+      /*
+       * Probably a corrupt capture file; don't blow up trying
+       * to allocate space for an immensely-large packet.
+       */
+      return 0;
+    }
     buffer=g_malloc(packet_size);
     r = file_read(buffer, 1, packet_size, wth->fh);
     g_free(buffer);