[FFmpeg-devel] [PATCH 1/2] avcodec/wmv2dec: Check end of bitstream in parse_mb_skip() and ff_wmv2_decode_mb()

[Michael Niedermayer]

Fixes: Timeout
Fixes: 3200/clusterfuzz-testcase-5750022136135680

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/wmv2dec.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/libavcodec/wmv2dec.c b/libavcodec/wmv2dec.c
index 20dbee5703..62291d4163 100644
--- a/libavcodec/wmv2dec.c
+++ b/libavcodec/wmv2dec.c
@@ -30,7 +30,7 @@
 #include "wmv2.h"
 
 
-static void parse_mb_skip(Wmv2Context *w)
+static int parse_mb_skip(Wmv2Context *w)
 {
     int mb_x, mb_y;
     MpegEncContext *const s = &w->s;
@@ -45,6 +45,8 @@ static void parse_mb_skip(Wmv2Context *w)
                     MB_TYPE_16x16 | MB_TYPE_L0;
         break;
     case SKIP_TYPE_MPEG:
+        if (get_bits_left(&s->gb) < s->mb_height * s->mb_width)
+            return AVERROR_INVALIDDATA;
         for (mb_y = 0; mb_y < s->mb_height; mb_y++)
             for (mb_x = 0; mb_x < s->mb_width; mb_x++)
                 mb_type[mb_y * s->mb_stride + mb_x] =
@@ -52,6 +54,8 @@ static void parse_mb_skip(Wmv2Context *w)
         break;
     case SKIP_TYPE_ROW:
         for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
+            if (get_bits_left(&s->gb) < 1)
+                return AVERROR_INVALIDDATA;
             if (get_bits1(&s->gb)) {
                 for (mb_x = 0; mb_x < s->mb_width; mb_x++)
                     mb_type[mb_y * s->mb_stride + mb_x] =
@@ -65,6 +69,8 @@ static void parse_mb_skip(Wmv2Context *w)
         break;
     case SKIP_TYPE_COL:
         for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
+            if (get_bits_left(&s->gb) < 1)
+                return AVERROR_INVALIDDATA;
             if (get_bits1(&s->gb)) {
                 for (mb_y = 0; mb_y < s->mb_height; mb_y++)
                     mb_type[mb_y * s->mb_stride + mb_x] =
@@ -77,6 +83,7 @@ static void parse_mb_skip(Wmv2Context *w)
         }
         break;
     }
+    return 0;
 }
 
 static int decode_ext_header(Wmv2Context *w)
@@ -170,9 +177,12 @@ int ff_wmv2_decode_secondary_picture_header(MpegEncContext *s)
         }
     } else {
         int cbp_index;
+        int ret;
         w->j_type = 0;
 
-        parse_mb_skip(w);
+        ret = parse_mb_skip(w);
+        if (ret < 0)
+            return ret;
         cbp_index = decode012(&s->gb);
         w->cbp_table_index = wmv2_get_cbp_table_index(s, cbp_index);
 
@@ -345,6 +355,12 @@ int ff_wmv2_decode_mb(MpegEncContext *s, int16_t block[6][64])
     if (w->j_type)
         return 0;
 
+    if (get_bits_left(&s->gb) < 0) {
+        av_log(s->avctx, AV_LOG_ERROR,
+                "Insufficient bits left at %d %d\n", s->mb_x, s->mb_y);
+        return AVERROR_INVALIDDATA;
+    }
+
     if (s->pict_type == AV_PICTURE_TYPE_P) {
         if (IS_SKIP(s->current_picture.mb_type[s->mb_y * s->mb_stride + s->mb_x])) {
             /* skip mb */
-- 
2.14.1