[FFmpeg-cvslog] avcodec/alsdec: Set channels from data after data is set

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Fri Mar 18 00:11:28 2022 +0100| [31916d3d9fc61bab50ccbcc2d58bf7e7efb6c8a0] | committer: Michael Niedermayer

avcodec/alsdec: Set channels from data after data is set

Fixes: out of array write
Fixes: 45624/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-6473487382872064
Fixes: 45626/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-4874997192065024

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: James Almer <jamrial at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=31916d3d9fc61bab50ccbcc2d58bf7e7efb6c8a0
---

 libavcodec/alsdec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index 822cf211b0..73af829178 100644
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -1986,7 +1986,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
     unsigned int c;
     unsigned int channel_size;
     int num_buffers, ret;
-    int channels = avctx->ch_layout.nb_channels;
+    int channels;
     ALSDecContext *ctx = avctx->priv_data;
     ALSSpecificConfig *sconf = &ctx->sconf;
     ctx->avctx = avctx;
@@ -2000,6 +2000,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
         av_log(avctx, AV_LOG_ERROR, "Reading ALSSpecificConfig failed.\n");
         return ret;
     }
+    channels = avctx->ch_layout.nb_channels;
 
     if ((ret = check_specific_config(ctx)) < 0) {
         return ret;