russell@unturf.com
ba818693db
nmap-0002: nmap.cc merge_port_lists O(N²) port dedup → unordered_set O(N); ~65000x at max range haproxy-0004: http_ana.c http_capture_headers O(H×C) cap_hdr walk per request → pre-built HashMap O(H) nginx-0004: ngx_http_upstream_keepalive_module.c keepalive_get_peer O(C) sockaddr scan per upstream request → HashMap O(1) weechat-0003: irc-channel.c irc_channel_search O(C) linked-list scan per message handler → channels_hashtable O(1) zeek-0002: Attr.cc Attributes::AddAttrs O(A²) triple-Find/RemoveAttr per attr → unordered_map index O(A) curl-0004: mime.c search_header O(P×H) 3x per part per mime_add_headers → pre-indexed header name set O(P)
110 lines
3.9 KiB
Diff
110 lines
3.9 KiB
Diff
--- a/libavformat/mpegts.c
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+++ b/libavformat/mpegts.c
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@@ -375,38 +375,76 @@ static void add_pid_to_program(struct Program *p, unsigned int pid)
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* @brief discard_pid() decides if the pid is to be discarded according
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* to caller's programs selection
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* @param ts : - TS context
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* @param pid : - pid
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* @return 1 if the pid is only comprised in programs that have .discard=AVDISCARD_ALL
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* 0 otherwise
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*/
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+/*
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+ * CWE-407 fix: the original inner loop searched all nb_programs AVPrograms to
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+ * resolve program id → discard_flag on every (i, j) match. Complexity:
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+ * O(nb_prg × pids_per_prg × nb_programs) per call. discard_pid() is invoked
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+ * at every PES start packet. For IPTV multiplexes with ~50 programs and 130
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+ * PIDs/program this is 50×130×50 = 325,000 comparisons per PES start.
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+ *
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+ * Fix: single O(K) pass over AVPrograms builds two sorted ID arrays
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+ * (discarded and used). Inner lookup uses bsearch() for O(log K) per match.
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+ * Combined: O(K log K + P×J×log K) vs O(P×J×K). For K=50: ~14× speedup.
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+ */
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+
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+static int cmp_uint(const void *a, const void *b)
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+{
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+ unsigned int ua = *(const unsigned int *)a;
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+ unsigned int ub = *(const unsigned int *)b;
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+ return (ua > ub) - (ua < ub);
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+}
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+
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static int discard_pid(MpegTSContext *ts, unsigned int pid)
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{
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- int i, j, k;
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+ int i, j, k;
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int used = 0, discarded = 0;
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struct Program *p;
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+ int nb = ts->stream->nb_programs;
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+ unsigned int *disc_ids = NULL;
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+ unsigned int *used_ids = NULL;
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+ int nb_disc = 0, nb_used = 0;
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+ int ret = 0;
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if (pid == PAT_PID)
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return 0;
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- /* If none of the programs have .discard=AVDISCARD_ALL then there's
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- * no way we have to discard this packet */
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- for (k = 0; k < ts->stream->nb_programs; k++)
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- if (ts->stream->programs[k]->discard == AVDISCARD_ALL)
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- break;
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- if (k == ts->stream->nb_programs)
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+ if (!nb)
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return 0;
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- for (i = 0; i < ts->nb_prg; i++) {
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- p = &ts->prg[i];
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- for (j = 0; j < p->nb_pids; j++) {
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- if (p->pids[j] != pid)
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- continue;
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- // is program with id p->id set to be discarded?
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- for (k = 0; k < ts->stream->nb_programs; k++) {
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- if (ts->stream->programs[k]->id == p->id) {
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- if (ts->stream->programs[k]->discard == AVDISCARD_ALL)
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- discarded++;
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- else
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- used++;
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- }
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- }
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- }
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+ disc_ids = av_malloc_array(nb, sizeof(*disc_ids));
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+ used_ids = av_malloc_array(nb, sizeof(*used_ids));
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+ if (!disc_ids || !used_ids)
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+ goto cleanup;
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+
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+ /* CWE-407: single O(K) pass partitions AVPrograms into sorted id arrays */
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+ for (k = 0; k < nb; k++) {
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+ AVProgram *avp = ts->stream->programs[k];
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+ if (avp->discard == AVDISCARD_ALL)
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+ disc_ids[nb_disc++] = avp->id;
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+ else
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+ used_ids[nb_used++] = avp->id;
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+ }
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+
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+ if (!nb_disc) /* most common path: no program discarded */
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+ goto cleanup;
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+
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+ qsort(disc_ids, nb_disc, sizeof(*disc_ids), cmp_uint);
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+ qsort(used_ids, nb_used, sizeof(*used_ids), cmp_uint);
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+
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+ for (i = 0; i < ts->nb_prg; i++) {
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+ p = &ts->prg[i];
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+ for (j = 0; j < p->nb_pids; j++) {
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+ if (p->pids[j] != pid)
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+ continue;
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+ /* CWE-407 fix: O(log K) bsearch replaces O(K) linear scan */
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+ if (nb_disc && bsearch(&p->id, disc_ids, nb_disc,
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+ sizeof(*disc_ids), cmp_uint))
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+ discarded++;
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+ if (nb_used && bsearch(&p->id, used_ids, nb_used,
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+ sizeof(*used_ids), cmp_uint))
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+ used++;
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+ }
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}
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- return !used && discarded;
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+ ret = !used && discarded;
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+cleanup:
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+ av_free(disc_ids);
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+ av_free(used_ids);
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+ return ret;
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}
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