[FFmpeg-cvslog] avformat/mlvdec: fix size checks

[Michael Niedermayer]

ffmpeg | branch: release/7.1 | Michael Niedermayer <michael at niedermayer.cc> | Fri Feb  7 02:33:21 2025 +0100| [2e7364727caa44ce040056f9498e1c0c93bb9511] | committer: Michael Niedermayer

avformat/mlvdec: fix size checks

Fixes: heap-buffer-overflow
Fixes: 391962476/clusterfuzz-testcase-minimized-ffmpeg_dem_MLV_fuzzer-5746746587676672

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 251d43aef0df9262f2688c1c848af993bbb67d08)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2e7364727caa44ce040056f9498e1c0c93bb9511
---

 libavformat/mlvdec.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/libavformat/mlvdec.c b/libavformat/mlvdec.c
index 985365326e..20a6f3629a 100644
--- a/libavformat/mlvdec.c
+++ b/libavformat/mlvdec.c
@@ -437,19 +437,25 @@ static int read_packet(AVFormatContext *avctx, AVPacket *pkt)
     if (size < 16)
         return AVERROR_INVALIDDATA;
     avio_skip(pb, 12); //timestamp, frameNumber
-    if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
+    size -= 12;
+    if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
+        if (size < 8)
+            return AVERROR_INVALIDDATA;
         avio_skip(pb, 8); // cropPosX, cropPosY, panPosX, panPosY
+        size -= 8;
+    }
     space = avio_rl32(pb);
+    if (size < space + 4LL)
+        return AVERROR_INVALIDDATA;
     avio_skip(pb, space);
+    size -= space;
 
     if ((mlv->class[st->id] & (MLV_CLASS_FLAG_DELTA|MLV_CLASS_FLAG_LZMA))) {
         ret = AVERROR_PATCHWELCOME;
     } else if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
         ret = av_get_packet(pb, pkt, (st->codecpar->width * st->codecpar->height * st->codecpar->bits_per_coded_sample + 7) >> 3);
     } else { // AVMEDIA_TYPE_AUDIO
-        if (space > UINT_MAX - 24 || size < (24 + space))
-            return AVERROR_INVALIDDATA;
-        ret = av_get_packet(pb, pkt, size - (24 + space));
+        ret = av_get_packet(pb, pkt, size - 4);
     }
 
     if (ret < 0)