Re: [FFmpeg-devel] [PATCH 1/7] avformat/mov_chan: Check for FF_SANE_NB_CHANNELS

[James Almer]

On 9/13/2024 2:48 PM, Michael Niedermayer wrote:

On Fri, Sep 13, 2024 at 12:08:45PM +0200, Anton Khirnov wrote:

Quoting Michael Niedermayer (2024-09-13 01:33:31)

We do not support more channels. For example avcodec_open2() limits channels 
this way too

The example file contains multiple chunks with over 16 million channels

We had this discussion already.

I remembered something too, but couldnt find the thread within teh time i was 
looking for it

Ad-hoc checks like this are only
addressing a symptom (probably one of many), and hide the actual bug.

If you have a better fix, submit it.

Does the following help with this sample?

diff --git a/libavformat/mov_chan.c b/libavformat/mov_chan.c
index cc5b333129..4484a22a10 100644
--- a/libavformat/mov_chan.c
+++ b/libavformat/mov_chan.c
@@ -543,10 +543,22 @@ int ff_mov_read_chan(AVFormatContext *s, AVIOContext *pb, 
AVStream *st,
         return 0;

     if (layout_tag == MOV_CH_LAYOUT_USE_DESCRIPTIONS) {
-        int nb_channels = ch_layout->nb_channels ? ch_layout->nb_channels : 
num_descr;
+        int nb_channels = ch_layout->nb_channels;
+
+        if (!num_descr || num_descr < nb_channels) {
+            av_log(s, AV_LOG_ERROR, "got %d channel descriptions when at least %d 
were needed\n",
+                   num_descr, nb_channels);
+            return AVERROR_INVALIDDATA;
+        }
+
         if (num_descr > nb_channels) {
-            av_log(s, AV_LOG_WARNING, "got %d channel descriptions, capping to the 
number of channels %d\n",
+            int strict = s->strict_std_compliance >= FF_COMPLIANCE_STRICT;
+            av_log(s, strict ? AV_LOG_ERROR : AV_LOG_WARNING,
+                   "got %d channel descriptions when number of channels is 
%d\n",
                    num_descr, nb_channels);
+            if (strict)
+                return AVERROR_INVALIDDATA;
+            av_log(s, AV_LOG_WARNING, "capping channel descriptions to the number 
of channels\n");
             num_descr = nb_channels;
         }

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