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@niedermayer.cc>

diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index 279cfe9412857606b0690882b8cd1a22ef535ba7..65e5203c317c35f0da99841ebe72b7a3b4d3e321 100644 (file)
--- 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;