mpegts: Do not try to write a PMT larger than SECTION_SIZE

Prevent out of array writes.

Similar to what Michael Niedermayer did to address the same issue.

Bug-Id: CVE-2014-2263
CC: libav-stable@libav.org
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavformat/mpegtsenc.c

@@ -226,7 +226,7 @@ static void mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
 {
     MpegTSWrite *ts = s->priv_data;
     uint8_t data[SECTION_LENGTH], *q, *desc_length_ptr, *program_info_length_ptr;
-    int val, stream_type, i;
+    int val, stream_type, i, err = 0;
 
     q = data;
     put16(&q, 0xe000 | service->pcr_pid);
@@ -244,6 +244,11 @@ static void mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
         AVStream *st = s->streams[i];
         MpegTSWriteStream *ts_st = st->priv_data;
         AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL, 0);
+
+        if (q - data > SECTION_LENGTH - 3 - 2 - 6) {
+            err = 1;
+            break;
+        }
         switch (st->codec->codec_id) {
         case AV_CODEC_ID_MPEG1VIDEO:
         case AV_CODEC_ID_MPEG2VIDEO:
@@ -301,6 +306,10 @@ static void mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
                 *len_ptr = 0;
 
                 for (p = lang->value; next && *len_ptr < 255 / 4 * 4; p = next + 1) {
+                    if (q - data > SECTION_LENGTH - 4) {
+                        err = 1;
+                        break;
+                    }
                     next = strchr(p, ',');
                     if (strlen(p) != 3 && (!next || next != p + 3))
                         continue; /* not a 3-letter code */
@@ -335,6 +344,12 @@ static void mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
             *q++ = language[1];
             *q++ = language[2];
             *q++ = 0x10; /* normal subtitles (0x20 = if hearing pb) */
+
+            if (q - data > SECTION_LENGTH - 4) {
+                err = 1;
+                break;
+            }
+
             if (st->codec->extradata_size == 4) {
                 memcpy(q, st->codec->extradata, 4);
                 q += 4;
@@ -360,6 +375,13 @@ static void mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
         desc_length_ptr[0] = val >> 8;
         desc_length_ptr[1] = val;
     }
+
+    if (err)
+        av_log(s, AV_LOG_ERROR,
+               "The PMT section cannot fit stream %d and all following streams.\n"
+               "Try reducing the number of languages in the audio streams "
+               "or the total number of streams.\n", i);
+
     mpegts_write_section1(&service->pmt, PMT_TID, service->sid, 0, 0, 0,
                           data, q - data);
 }