avcodec/alsdec: Limit maximum channels to 512

There seems to be no limit in the specification and upto 64k could be stored
512 is choosen as limit as thats the maximum in a conformance sample

An alternative to this patch would be a max_channels variable

Fixes: OOM
Fixes: 16200/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5764788793114624
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Suggested-by: Thilo Borgmann <thilo.borgmann@mail.de>
Reviewed-by: Thilo Borgmann <thilo.borgmann@mail.de>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index 26c496c769b0a9391de55929b26df876c1a04c94..1fdd0cb0fe07d7817d1de8a2d6235f4a2ed0a16c 100644 (file)
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -348,6 +348,11 @@ static av_cold int read_specific_config(ALSDecContext *ctx)
     if (als_id != MKBETAG('A','L','S','\0'))
         return AVERROR_INVALIDDATA;
 
+    if (avctx->channels > FF_SANE_NB_CHANNELS) {
+        avpriv_request_sample(avctx, "Huge number of channels\n");
+        return AVERROR_PATCHWELCOME;
+    }
+
     ctx->cur_frame_length = sconf->frame_length;
 
     // read channel config