This is a more appropriate place than a function designed to reconstruct a macroblock. It furthermore limits these checks to the codecs that actually need it (and removes it from e.g. RV10 and RV20 -- the latter actually uses these buffers, but only for intra-frames, so they don't need to be cleaned manually). This furthermore means that ff_mpv_reconstruct_mb() and therefore also the error-resilience code no longer needs block_index set. This fixes a crash caused by 65d5ccb808ec93de46a2458ea8cc082ce4460f34 when ff_mpv_reconstruct_mb() is called by VC-1 code without block_index being initialized properly (VC-1 uses and initializes block_index itself normally). Fixes: 69814/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1_fuzzer-4868081575329792 Fixes: heap-buffer-overflow
Showing the changes to libavcodec (2 of 2 files). Show all
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| @@ -271,6 +271,15 @@ static int decode_slice(MpegEncContext *s) · 270 unmodified lines | ||
| 271 | 271 | ff_tlog(NULL, "Decoding MB at %dx%d\n", s->mb_x, s->mb_y); |
| 272 | 272 | ret = s->decode_mb(s, s->block); |
| 273 | 273 | |
| 274 | + if (s->h263_pred || s->h263_aic) { | |
| 275 | + int mb_xy = s->mb_y * s->mb_stride + s->mb_x; | |
| 276 | + if (!s->mb_intra) { | |
| 277 | + if (s->mbintra_table[mb_xy]) | |
| 278 | + ff_clean_intra_table_entries(s); | |
| 279 | + } else | |
| 280 | + s->mbintra_table[mb_xy] = 1; | |
| 281 | + } | |
| 282 | + | |
| 274 | 283 | if (s->pict_type != AV_PICTURE_TYPE_B) |
| 275 | 284 | ff_h263_update_motion_val(s); |
| 276 | 285 | |
| @@ -61,6 +61,7 @@ void mpv_reconstruct_mb_internal(MpegEncContext *s, int16_t block[12][64], · 60 unmodified lines | ||
| 61 | 61 | |
| 62 | 62 | s->cur_pic.qscale_table[mb_xy] = s->qscale; |
| 63 | 63 | |
| 64 | +#if IS_ENCODER | |
| 64 | 65 | /* update DC predictors for P macroblocks */ |
| 65 | 66 | if (!s->mb_intra) { |
| 66 | 67 | if (is_mpeg12 != DEFINITELY_MPEG12_H261 && (s->h263_pred || s->h263_aic)) { |
| @@ -70,7 +71,6 @@ void mpv_reconstruct_mb_internal(MpegEncContext *s, int16_t block[12][64], · 3 unmodified lines | ||
| 70 | 71 | } else if (is_mpeg12 != DEFINITELY_MPEG12_H261 && (s->h263_pred || s->h263_aic)) |
| 71 | 72 | s->mbintra_table[mb_xy] = 1; |
| 72 | 73 | |
| 73 | −#if IS_ENCODER | |
| 74 | 74 | if ((s->avctx->flags & AV_CODEC_FLAG_PSNR) || s->frame_skip_threshold || s->frame_skip_factor || |
| 75 | 75 | !((s->intra_only || s->pict_type == AV_PICTURE_TYPE_B) && |
| 76 | 76 | s->avctx->mb_decision != FF_MB_DECISION_RD)) // FIXME precalc |