lib/51952: libpcap fault applying filter to unactivated handle

[bch <brad.harder%gmail.com@localhost>]

>Number:         51952
>Category:       lib
>Synopsis:       libpcap will fault if an attempt to apply a filter on non-activated handle occurs.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Feb 05 20:55:00 +0000 2017
>Originator:     bch <brad.harder%gmail.com@localhost>
>Release:        NetBSD 7.99.59
>Organization:
	method logic digital
>Environment:
System: NetBSD kamloops 7.99.59 NetBSD 7.99.59 (MODULAR) #51: Sun Feb
5 09:44:00 PST 2017
root@kamloops:/usr/src/sys/arch/amd64/compile/obj/MODULAR amd64
Architecture: x86_64
Machine: amd64
>Description:
libpcap faults if one tries to apply a filter to an unactivated pcap handle.
>How-To-Repeat:
        ...
        char errbuf[PCAP_ERRBUF_SIZE];
        struct bpf_program fp;

        pcap_t *handle = pcap_create("wm0", errbuf);
	pcap_compile(handle, &fp, "port 80", 0, PCAP_NETMASK_UNKNOWN); /* not
yet activated... */
        // segfault in freechunks()
>Fix:

The compiler state "chunks" initialization is short-circuited if
the handle is not activated, but the chunks cleanup is unconditional.
Unconditionally initializing allows cleanup in case of error-state
to happen fault-free.

nb: patch already submitted upstream to the-tcpdump-group.

FIX
===

--- ./external/bsd/libpcap/dist/gencode.old     2017-02-05
12:34:30.181700021 -0800
+++ ./external/bsd/libpcap/dist/gencode.c       2017-02-05
12:35:03.506099929 -0800
@@ -688,13 +688,13 @@
         * If this pcap_t hasn't been activated, it doesn't have a
         * link-layer type, so we can't use it.
         */
+       initchunks(&cstate);
        if (!p->activated) {
                pcap_snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                    "not-yet-activated pcap_t passed to pcap_compile");
                rc = -1;
                goto quit;
        }
-       initchunks(&cstate);
        cstate.no_optimize = 0;
        cstate.ai = NULL;
        cstate.ic.root = NULL;