[FFmpeg-cvslog] avcodec/exr: Check oe in huf_decode() before use

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Mar 30 09:15:27 2021 +0200| [9e8475c7c7a81e8299e88d89981df3c14657fff4] | committer: Michael Niedermayer

avcodec/exr: Check oe in huf_decode() before use

Fixes: out of array access
Fixes: 31386/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EXR_fuzzer-5773234709594112

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=9e8475c7c7a81e8299e88d89981df3c14657fff4
---

 libavcodec/exr.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index 279cfe9412..65e5203c31 100644
--- a/libavcodec/exr.c
+++ b/libavcodec/exr.c
@@ -422,7 +422,12 @@ static int huf_decode(VLC *vlc, GetByteContext *gb, int nbits, int run_sym,
 
         if (x == run_sym) {
             int run = get_bits(&gbit, 8);
-            uint16_t fill = out[oe - 1];
+            uint16_t fill;
+
+            if (oe == 0 || oe + run > no)
+                return AVERROR_INVALIDDATA;
+
+            fill = out[oe - 1];
 
             while (run-- > 0)
                 out[oe++] = fill;