[FFmpeg-cvslog] avformat/mpegts: fixes overflow when parsing the PMT

[Nicolas Jorge Dato]

ffmpeg | branch: master | Nicolas Jorge Dato <nicolas.dato at gmail.com> | Wed Sep 15 09:58:11 2021 -0300| [5a0a9f78252825dfe1824eedbc373aea443e5e77] | committer: Marton Balint

avformat/mpegts: fixes overflow when parsing the PMT

When a possible overflow was detected, there was a break to exit the while
loop. However, it should have already substracted 2 bytes from
program_info_length (descriptor ID + length).

Fixes ticket #9422.

Signed-off-by: Marton Balint <cus at passwd.hu>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5a0a9f78252825dfe1824eedbc373aea443e5e77
---

 libavformat/mpegts.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index ed918cb356..da8eee2414 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2355,10 +2355,11 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
 
         av_log(ts->stream, AV_LOG_TRACE, "program tag: 0x%02x len=%d\n", tag, len);
 
-        if (len > program_info_length - 2)
+        program_info_length -= 2;
+        if (len > program_info_length)
             // something else is broken, exit the program_descriptors_loop
             break;
-        program_info_length -= len + 2;
+        program_info_length -= len;
         if (tag == IOD_DESCRIPTOR) {
             get8(&p, p_end); // scope
             get8(&p, p_end); // label