[Copilot]

This fixes CVE-2022-47012. When opening a pcap device fails, gen_eth_init (common/gen_eth.c) prints pcap_errbuf. That buffer is never initialized, and libpcap doesn't promise to write it on every failure. In that case %s prints leftover stack memory. Without a terminating NUL, it can also read past the end of the buffer.

Changes (common/gen_eth.c)

• gen_eth_init
  • pcap_errbuf is zero-initialized, and its last byte is set to NUL again before it is printed.
  • p starts out as NULL.
  • A NULL device is rejected before reaching pcap_open_live/pcap_open.
• gen_eth_show_dev_list: pcap_errbuf is zero-initialized the same way.

char pcap_errbuf[PCAP_ERRBUF_SIZE] = { 0 };
...
pcap_error:
   pcap_errbuf[PCAP_ERRBUF_SIZE - 1] = '\0';
   fprintf(stderr, "gen_eth_init: unable to open device '%s' with PCAP (%s)\n", device, pcap_errbuf);

For reviewers

• When libpcap does fill the buffer, the error message is unchanged.
• The change is in the commit titled "Plan: fix CVE-2022-47012". Squash or reword it when merging.

• Fixes dynamipsv0.2.25: 1 vulnerabilities (highest severity is: 7.5) #319