[FFmpeg-devel] [PATCH] avcodec/scpr: Fix reading a pixel before the first

[Michael Niedermayer]

Fixes: 5540/clusterfuzz-testcase-minimized-6122458273808384

Found-by: continuous fuzzing process 
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
---
 libavcodec/scpr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavcodec/scpr.c b/libavcodec/scpr.c
index cbe1bc40d9..ad6073dbf0 100644
--- a/libavcodec/scpr.c
+++ b/libavcodec/scpr.c
@@ -681,6 +681,8 @@ static int decompress_p(AVCodecContext *avctx,
                                 return AVERROR_INVALIDDATA;
 
                             if (bx == 0) {
+                                if (by < 2)
+                                    return AVERROR_INVALIDDATA;
                                 z = backstep;
                             } else {
                                 z = 0;
@@ -710,6 +712,8 @@ static int decompress_p(AVCodecContext *avctx,
                                 return AVERROR_INVALIDDATA;
 
                             if (bx == 0) {
+                                if (by < 2)
+                                    return AVERROR_INVALIDDATA;
                                 z = backstep;
                             } else {
                                 z = 0;
-- 
2.16.1

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