heap-buffer-overflow at libavfilter/vf_bwdif.c:133

[Suhwan]

Summary of the bug:
There is a heap-buffer-overflow at libavfilter/vf_bwdif.c:133 in filter_intra

I compiled ffmpeg with "--toolchain=clang-asan" to check the memory corruption and attached log file.
How to reproduce:

% ffmpeg_g -y -i $PoC -filter_complex bwdif -target dvd -loglevel 99 tmp.h263

ffmpeg version N-95336-g4f4334bcbc Copyright (c) 2000-2019 the FFmpeg developers
built with clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
configuration: --cc=clang --cxx=clang++ --ld=clang --enable-debug --toolchain=clang-asan

Here's ASAN log

=================================================================
==15693==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x619000002d60 at pc 0x000000a79550 bp 0x7fffffffb4a0 sp 0x7fffffffb498
READ of size 1 at 0x619000002d60 thread T0
    #0 0xa7954f in filter_intra ffmpeg/libavfilter/vf_bwdif.c:133:5
    #1 0xa816b4 in filter_slice ffmpeg/libavfilter/vf_bwdif.c:236:17
    #2 0x942579 in worker_func ffmpeg/libavfilter/pthread.c:50:15
    #3 0x868c042 in run_jobs ffmpeg/libavutil/slicethread.c:61:9
    #4 0x868b6e4 in avpriv_slicethread_execute ffmpeg/libavutil/slicethread.c:188:19
    #5 0x941cd6 in thread_execute ffmpeg/libavfilter/pthread.c:72:5
    #6 0xa73691 in filter ffmpeg/libavfilter/vf_bwdif.c:283:9
    #7 0x163bd0c in return_frame ffmpeg/libavfilter/yadif_common.c:51:5
    #8 0x163ddf9 in ff_yadif_request_frame ffmpeg/libavfilter/yadif_common.c:166:9
    #9 0x831204 in ff_request_frame_to_filter ffmpeg/libavfilter/avfilter.c:458:15
    #10 0x826f74 in ff_filter_activate ffmpeg/libavfilter/avfilter.c:1280:20
    #11 0x864092 in get_frame_internal ffmpeg/libavfilter/buffersink.c:110:19
    #12 0x84bd53 in avfilter_graph_request_oldest ffmpeg/libavfilter/avfiltergraph.c:1409:17
    #13 0x5e3d0d in transcode_from_filter ffmpeg/fftools/ffmpeg.c:4531:11
    #14 0x5e3d0d in transcode_step ffmpeg/fftools/ffmpeg.c:4606
    #15 0x5e3d0d in transcode ffmpeg/fftools/ffmpeg.c:4682
    #16 0x5db65b in main ffmpeg/fftools/ffmpeg.c:4884:9
    #17 0x7ffff5c93b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #18 0x41def9 in _start (ffmpeg_asan+0x41def9)

0x619000002d60 is located 32 bytes to the left of 1055-byte region [0x619000002d80,0x61900000319f)
allocated by thread T0 here:
    #0 0x4de9e8 in posix_memalign (ffmpeg_asan+0x4de9e8)
    #1 0x8598211 in av_malloc ffmpeg/libavutil/mem.c:87:9
    #2 0x84ff141 in av_buffer_alloc ffmpeg/libavutil/buffer.c:72:12
    #3 0x84ff141 in av_buffer_allocz ffmpeg/libavutil/buffer.c:85
    #4 0x8503966 in pool_alloc_buffer ffmpeg/libavutil/buffer.c:313:26
    #5 0x8503966 in av_buffer_pool_get ffmpeg/libavutil/buffer.c:349
    #6 0x91ab2d in ff_frame_pool_get ffmpeg/libavfilter/framepool.c:222:29
    #7 0x15d770c in ff_default_get_video_buffer ffmpeg/libavfilter/video.c:90:13
    #8 0x124c5c9 in scale_frame ffmpeg/libavfilter/vf_scale.c:460:11
    #9 0x124a6bc in filter_frame ffmpeg/libavfilter/vf_scale.c:549:11
    #10 0x826e29 in ff_filter_activate_default ffmpeg/libavfilter/avfilter.c:1071:11
    #11 0x826e29 in ff_filter_activate ffmpeg/libavfilter/avfilter.c:1430
    #12 0x86fcd5 in push_frame ffmpeg/libavfilter/buffersrc.c:187:15
    #13 0x86fcd5 in av_buffersrc_add_frame_internal ffmpeg/libavfilter/buffersrc.c:261
    #14 0x86e762 in av_buffersrc_add_frame_flags ffmpeg/libavfilter/buffersrc.c:170:16
    #15 0x666407 in ifilter_send_frame ffmpeg/fftools/ffmpeg.c:2186:11
    #16 0x666407 in send_frame_to_filters ffmpeg/fftools/ffmpeg.c:2260
    #17 0x607666 in decode_video ffmpeg/fftools/ffmpeg.c:2459:11
    #18 0x607666 in process_input_packet ffmpeg/fftools/ffmpeg.c:2613
    #19 0x64a707 in process_input ffmpeg/fftools/ffmpeg.c:4508:5
    #20 0x5e7157 in transcode_step ffmpeg/fftools/ffmpeg.c:4628:11
    #21 0x5e7157 in transcode ffmpeg/fftools/ffmpeg.c:4682
    #22 0x5db65b in main ffmpeg/fftools/ffmpeg.c:4884:9
    #23 0x7ffff5c93b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310

SUMMARY: AddressSanitizer: heap-buffer-overflow ffmpeg/libavfilter/vf_bwdif.c:133:5 in filter_intra

Please confirm.
Thanks

[Suhwan]

poc