On 4/30/2024 9:38 PM, Michael Niedermayer wrote:
On Tue, Apr 30, 2024 at 06:27:23PM -0300, James Almer wrote:
On 4/29/2024 9:48 PM, Michael Niedermayer wrote:
Fixes: division by 0
Fixes: decoder modifying demuxer channels on failure
Fixes: -sseof -5 -i zgclab/ffmpeg_crash/poc3
Found-by: Wang Dawei and Zhou Geng, from Zhongguancun Laboratory
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
---
libavutil/opt.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/libavutil/opt.c b/libavutil/opt.c
index ecbf7efe5fb..24c08e4bc06 100644
--- a/libavutil/opt.c
+++ b/libavutil/opt.c
@@ -132,9 +132,11 @@ static void opt_free_elem(const AVOption *o, void *ptr)
av_dict_free((AVDictionary **)ptr);
break;
- case AV_OPT_TYPE_CHLAYOUT:
+ case AV_OPT_TYPE_CHLAYOUT: {
+ int nb_channels = ((AVChannelLayout *)ptr)->nb_channels;
av_channel_layout_uninit((AVChannelLayout *)ptr);
- break;
+ ((AVChannelLayout *)ptr)->nb_channels = nb_channels;
+ break;}
default:
break;
A little bit of context would be helpful here. What's using nb_channels
after av_opt_free was called and where?
demuxer sets nb_channels
find stream info copies codec params to context
find stream info tries opening decoder
decoder, refuses, and opt_free_elem() is called on cleanup
context now has 0 channels
context gets copied into params of demuxer
Should this happen if the internal decoder failed to generate a frame?
Can it be avoided?
demuxer goes like i have set the channels to a non zero value let me devide by
them
and oops
there is more than one position in this chain of events this can be fixed
thx
[...]
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