[FFmpeg-cvslog] avcodec/wmalosslessdec: move channel check up

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Wed Jan 15 00:32:55 2020 +0100| [891bcc4acc93e0c5a75ab7a9da668df84a0edba7] | committer: Michael Niedermayer

avcodec/wmalosslessdec: move channel check up

Fixes: out of array access
Fixes: 2nd part of 18429/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMALOSSLESS_fuzzer-6210814364614656

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=891bcc4acc93e0c5a75ab7a9da668df84a0edba7
---

 libavcodec/wmalosslessdec.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/libavcodec/wmalosslessdec.c b/libavcodec/wmalosslessdec.c
index d2f9d4a70f..2b97c2a848 100644
--- a/libavcodec/wmalosslessdec.c
+++ b/libavcodec/wmalosslessdec.c
@@ -189,6 +189,16 @@ static av_cold int decode_init(AVCodecContext *avctx)
         return AVERROR(EINVAL);
     }
 
+    if (avctx->channels < 0) {
+        av_log(avctx, AV_LOG_ERROR, "invalid number of channels %d\n",
+               avctx->channels);
+        return AVERROR_INVALIDDATA;
+    } else if (avctx->channels > WMALL_MAX_CHANNELS) {
+        avpriv_request_sample(avctx,
+                              "More than %d channels", WMALL_MAX_CHANNELS);
+        return AVERROR_PATCHWELCOME;
+    }
+
     s->max_frame_size = MAX_FRAMESIZE * avctx->channels;
     s->frame_data = av_mallocz(s->max_frame_size + AV_INPUT_BUFFER_PADDING_SIZE);
     if (!s->frame_data)
@@ -267,16 +277,6 @@ static av_cold int decode_init(AVCodecContext *avctx)
                 ++s->lfe_channel;
     }
 
-    if (s->num_channels < 0) {
-        av_log(avctx, AV_LOG_ERROR, "invalid number of channels %"PRId8"\n",
-               s->num_channels);
-        return AVERROR_INVALIDDATA;
-    } else if (s->num_channels > WMALL_MAX_CHANNELS) {
-        avpriv_request_sample(avctx,
-                              "More than %d channels", WMALL_MAX_CHANNELS);
-        return AVERROR_PATCHWELCOME;
-    }
-
     s->frame = av_frame_alloc();
     if (!s->frame)
         return AVERROR(ENOMEM);