[FFmpeg-cvslog] avcodec/pngdec: Check amount decoded

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sat Aug 17 23:55:34 2019 +0200| [861183f2e655ad5d399a8a23b6b6b48463962c5e] | committer: Michael Niedermayer

avcodec/pngdec: Check amount decoded

Fixes: Timeout (70sec -> 243ms)
Fixes: 16097/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APNG_fuzzer-5664690889293824
Fixes: 16927/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APNG_fuzzer-5170612070252544
Fixes: 16927/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APNG_fuzzer-5706325622784000
Fixes: 18705/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APNG_fuzzer-5650989302677504

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=861183f2e655ad5d399a8a23b6b6b48463962c5e
---

 libavcodec/pngdec.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index d37dabcc4d..3ce980fc15 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -320,6 +320,15 @@ static void deloco_ ## NAME(TYPE *dst, int size, int alpha) \
 YUV2RGB(rgb8, uint8_t)
 YUV2RGB(rgb16, uint16_t)
 
+static int percent_missing(PNGDecContext *s)
+{
+    if (s->interlace_type) {
+        return 100 - 100 * s->pass / (NB_PASSES - 1);
+    } else {
+        return 100 - 100 * s->y / s->cur_h;
+    }
+}
+
 /* process exactly one decompressed row */
 static void png_handle_row(PNGDecContext *s)
 {
@@ -1354,6 +1363,9 @@ exit_loop:
         return 0;
     }
 
+    if (percent_missing(s) > avctx->discard_damaged_percentage)
+        return AVERROR_INVALIDDATA;
+
     if (s->bits_per_pixel <= 4)
         handle_small_bpp(s, p);