Right now it is possible for the pointer for the current frame to be set in the context even when it could not be properly set up; this does not influence the ordinary ref frames, but only VP8Context.prev_frame. And since this code has been ported to the ProgressFrame API in d48d7bc434f30dfbdf346f16715e4f2044b3e000, this leads to segfaults, because the ProgressFrame API is less forgiving than the ThreadFrame API (waiting on an uninitialized ProgressFrame segfaults, waiting on an uninitialized ThreadFrame is a no-op (the code behaves as if frame-threading is not in use)). Fix this by maintaining the consistency of the frame pointers in the context (by setting them later). Fixes: NULL pointer dereference Fixes: 68192/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP8_fuzzer-6180311026171904
Unified · Split
| @@ -541,9 +541,12 @@ static int vp7_fade_frame(VP8Context *s, int alpha, int beta) · 540 unmodified lines | ||
| 541 | 541 | |
| 542 | 542 | /* preserve the golden frame, write a new previous frame */ |
| 543 | 543 | if (s->framep[VP8_FRAME_GOLDEN] == s->framep[VP8_FRAME_PREVIOUS]) { |
| 544 | − s->framep[VP8_FRAME_PREVIOUS] = vp8_find_free_buffer(s); | |
| 545 | − if ((ret = vp8_alloc_frame(s, s->framep[VP8_FRAME_PREVIOUS], 1)) < 0) | |
| 544 | + VP8Frame *prev_frame = vp8_find_free_buffer(s); | |
| 545 | + | |
| 546 | + ret = vp8_alloc_frame(s, prev_frame, 1); | |
| 547 | + if (ret < 0) | |
| 546 | 548 | return ret; |
| 549 | + s->framep[VP8_FRAME_PREVIOUS] = prev_frame; | |
| 547 | 550 | |
| 548 | 551 | dst = s->framep[VP8_FRAME_PREVIOUS]->tf.f; |
| 549 | 552 | |
| @@ -2675,8 +2678,6 @@ int vp78_decode_frame(AVCodecContext *avctx, AVFrame *rframe, int *got_frame, · 2125 unmodified lines | ||
| 2675 | 2678 | &s->frames[i] != s->framep[VP8_FRAME_ALTREF]) |
| 2676 | 2679 | vp8_release_frame(&s->frames[i]); |
| 2677 | 2680 | |
| 2678 | − curframe = s->framep[VP8_FRAME_CURRENT] = vp8_find_free_buffer(s); | |
| 2679 | − | |
| 2680 | 2681 | if (!s->colorspace) |
| 2681 | 2682 | avctx->colorspace = AVCOL_SPC_BT470BG; |
| 2682 | 2683 | if (s->fullrange) |
| @@ -2697,8 +2698,10 @@ int vp78_decode_frame(AVCodecContext *avctx, AVFrame *rframe, int *got_frame, · 14 unmodified lines | ||
| 2697 | 2698 | goto err; |
| 2698 | 2699 | } |
| 2699 | 2700 | |
| 2701 | + curframe = vp8_find_free_buffer(s); | |
| 2700 | 2702 | if ((ret = vp8_alloc_frame(s, curframe, referenced)) < 0) |
| 2701 | 2703 | goto err; |
| 2704 | + s->framep[VP8_FRAME_CURRENT] = curframe; | |
| 2702 | 2705 | if (s->keyframe) |
| 2703 | 2706 | curframe->tf.f->flags |= AV_FRAME_FLAG_KEY; |
| 2704 | 2707 | else |