#ffmpeg: Backport an upstreamed patch

From f5f2209d689cd17f4bce7ce5c4f0b1634befc785 Mon Sep 17 00:00:00 2001
From: Xiaohan Wang <xhwang@chromium.org>
Date: Fri, 23 Feb 2018 17:04:41 -0800
Subject: [PATCH] ffmpeg: Fix memset size on ctts_data in mov_read_trun()
 (round 2)

The allocated size of sc->ctts_data is
(st->nb_index_entries + entries) * sizeof(*sc->ctts_data).

The size to memset at offset sc->ctts_data + sc->ctts_count should be
(st->nb_index_entries + entries - sc->ctts_count) *
sizeof(*sc->ctts_data))

The current code missed |entries| I believe, which was introduced in
https://patchwork.ffmpeg.org/patch/5541/.

However, after offline discussion, it seems the original code is much
more clear to read (before https://patchwork.ffmpeg.org/patch/5541/).

Hence this CL revert the memset logic to it's previous state by
remembering the |old_ctts_allocated_size|, and only memset the newly
allocated entries.

BUG=812567

Change-Id: Ibe94c7138e5818bfaae76866bfa6619a9b8a2b6b
Reviewed-on: https://chromium-review.googlesource.com/934925
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/mov.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 04567fc475..f01116874c 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4596,6 +4596,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     int64_t prev_dts = AV_NOPTS_VALUE;
     int next_frag_index = -1, index_entry_pos;
     size_t requested_size;
+    size_t old_ctts_allocated_size;
     AVIndexEntry *new_entries;
     MOVFragmentStreamInfo * frag_stream_info;
 
@@ -4688,6 +4689,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     st->index_entries= new_entries;
 
     requested_size = (st->nb_index_entries + entries) * sizeof(*sc->ctts_data);
+    old_ctts_allocated_size = sc->ctts_allocated_size;
     ctts_data = av_fast_realloc(sc->ctts_data, &sc->ctts_allocated_size,
                                 requested_size);
     if (!ctts_data)
@@ -4697,8 +4699,8 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     // In case there were samples without ctts entries, ensure they get
     // zero valued entries. This ensures clips which mix boxes with and
     // without ctts entries don't pickup uninitialized data.
-    memset(sc->ctts_data + sc->ctts_count, 0,
-           (st->nb_index_entries - sc->ctts_count) * sizeof(*sc->ctts_data));
+    memset((uint8_t*)(sc->ctts_data) + old_ctts_allocated_size, 0,
+           sc->ctts_allocated_size - old_ctts_allocated_size);
 
     if (index_entry_pos < st->nb_index_entries) {
         // Make hole in index_entries and ctts_data for new samples
-- 
2.20.1

