[FFmpeg-cvslog] avcodec/eatgq: : Check index increments in tgq_decode_block()

[Michael Niedermayer]

ffmpeg | branch: release/4.3 | Michael Niedermayer <michael at niedermayer.cc> | Wed Jan 11 23:05:55 2023 +0100| [54635b3b98ea122c2388442cdf9484764104056a] | committer: Michael Niedermayer

avcodec/eatgq: : Check index increments in tgq_decode_block()

Fixes: out of array access
Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EATGQ_fuzzer-6743211456724992

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 e7755b433e913e32bb061f17d5ecfcbcfef995b7)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=54635b3b98ea122c2388442cdf9484764104056a
---

 libavcodec/eatgq.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/libavcodec/eatgq.c b/libavcodec/eatgq.c
index 1308c07cff..46bf226f6a 100644
--- a/libavcodec/eatgq.c
+++ b/libavcodec/eatgq.c
@@ -58,7 +58,7 @@ static av_cold int tgq_decode_init(AVCodecContext *avctx)
     return 0;
 }
 
-static void tgq_decode_block(TgqContext *s, int16_t block[64], GetBitContext *gb)
+static int tgq_decode_block(TgqContext *s, int16_t block[64], GetBitContext *gb)
 {
     uint8_t *perm = s->scantable.permutated;
     int i, j, value;
@@ -66,6 +66,8 @@ static void tgq_decode_block(TgqContext *s, int16_t block[64], GetBitContext *gb
     for (i = 1; i < 64;) {
         switch (show_bits(gb, 3)) {
         case 4:
+            if (i >= 63)
+                return AVERROR_INVALIDDATA;
             block[perm[i++]] = 0;
         case 0:
             block[perm[i++]] = 0;
@@ -75,6 +77,8 @@ static void tgq_decode_block(TgqContext *s, int16_t block[64], GetBitContext *gb
         case 1:
             skip_bits(gb, 2);
             value = get_bits(gb, 6);
+            if (value > 64 - i)
+                return AVERROR_INVALIDDATA;
             for (j = 0; j < value; j++)
                 block[perm[i++]] = 0;
             break;
@@ -102,6 +106,7 @@ static void tgq_decode_block(TgqContext *s, int16_t block[64], GetBitContext *gb
         }
     }
     block[0] += 128 << 4;
+    return 0;
 }
 
 static void tgq_idct_put_mb(TgqContext *s, int16_t (*block)[64], AVFrame *frame,
@@ -161,8 +166,11 @@ static int tgq_decode_mb(TgqContext *s, AVFrame *frame, int mb_y, int mb_x)
         if (ret < 0)
             return ret;
 
-        for (i = 0; i < 6; i++)
-            tgq_decode_block(s, s->block[i], &gb);
+        for (i = 0; i < 6; i++) {
+            int ret = tgq_decode_block(s, s->block[i], &gb);
+            if (ret < 0)
+                return ret;
+        }
         tgq_idct_put_mb(s, s->block, frame, mb_x, mb_y);
         bytestream2_skip(&s->gb, mode);
     } else {