On 31.10.2016 19:20, Sasi Inguva wrote:
> First of all, if nb_old == 0 i.e. there are no entries in AVIndex, then
> there is no point in calling mov_fix_index function at all. So instead of
> doing the above , you can directly check for st->nb_index_entries > 0 at
> the top of mov_fix_index and return otherwise.
OK, patch doing that is attached.
> Also, I don't understand how nb_old==0 can cause heap overflow. If I read
> the code correctly, if nb_old==0 find_prev_closest_keyframe_index , should
> return -1, which would make the function skip that edit list here
>
> if (index == -1) {
> av_log(mov>->fc, AV_LOG_ERROR, "Missing key frame while reordering
> index according to edit list\n");
> continue;
> }
This checks is four lines below the heap buffer overflow, which is obviously
too late.
Best regards,
Andreas
>From 634682d0628d02a2941140800e901611bfee2d0c Mon Sep 17 00:00:00 2001
From: Andreas Cadhalpun <[email protected]>
Date: Tue, 1 Nov 2016 01:05:01 +0100
Subject: [PATCH] mov: immediately return from mov_fix_index without old index
entries
If there are no index entries, e_old = st->index_entries is only one
byte large, since it was created by av_realloc called with size 0.
Thus accessing e_old[0].timestamp causes a heap buffer overflow.
Signed-off-by: Andreas Cadhalpun <[email protected]>
---
libavformat/mov.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 414007e..7614632 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2961,7 +2961,7 @@ static void mov_fix_index(MOVContext *mov, AVStream *st)
int first_non_zero_audio_edit = -1;
int packet_skip_samples = 0;
- if (!msc->elst_data || msc->elst_count <= 0) {
+ if (!msc->elst_data || msc->elst_count <= 0 || nb_old <= 0) {
return;
}
// Clean AVStream from traces of old index
--
2.10.1
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