avcodec/cbs: ensure user_data is padded for GBC parsing

Fixes crash noticed in the cbs_userdata patchset.

====ERROR: AddressSanitizer: heap-buffer-overflow on address 0x609000026c89 at pc 0x00010725d37b bp 0x7ffeea04e750 sp 0x7ffeea04e748
READ of size 4 at 0x609000026c89 thread T0
    #0 0x10725d37a in ff_cbs_read_unsigned get_bits.h:274
    #1 0x1072d2767 in ff_cbs_read_a53_user_data cbs_misc_syntax_template.c:119
    #2 0x1078251a7 in h264_metadata_filter h264_metadata_bsf.c:595
    #3 0x105c1321d in output_packet ffmpeg.c:853

0x609000026c89 is located 1 bytes to the right of 8-byte region [0x609000026c80,0x609000026c88)
allocated by thread T0 here:
    #0 0x10aef08d7 in wrap_posix_memalign (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x578d7)
    #1 0x10aca95e6 in av_malloc mem.c:87
    #2 0x10ac545fe in av_buffer_allocz buffer.c:72
    #3 0x107263b27 in cbs_h264_read_nal_unit cbs_h264_syntax_template.c:722
    #4 0x10725b688 in cbs_read_fragment_content cbs.c:155

Signed-off-by: Aman Gupta <aman@tmm1.net>
2 files changed
tree: 0c3dbb9f2fe7fcdfb1c0b37abee72432520bf61d
  1. .gitattributes
  2. .gitignore
  3. .travis.yml
  4. CONTRIBUTING.md
  5. COPYING.GPLv2
  6. COPYING.GPLv3
  7. COPYING.LGPLv2.1
  8. COPYING.LGPLv3
  9. CREDITS
  10. Changelog
  11. INSTALL.md
  12. LICENSE.md
  13. MAINTAINERS
  14. Makefile
  15. README.md
  16. RELEASE
  17. compat/
  18. configure
  19. doc/
  20. ffbuild/
  21. fftools/
  22. libavcodec/
  23. libavdevice/
  24. libavfilter/
  25. libavformat/
  26. libavresample/
  27. libavutil/
  28. libpostproc/
  29. libswresample/
  30. libswscale/
  31. presets/
  32. tests/
  33. tools/
README.md

FFmpeg README

FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.

Libraries

  • libavcodec provides implementation of a wider range of codecs.
  • libavformat implements streaming protocols, container formats and basic I/O access.
  • libavutil includes hashers, decompressors and miscellaneous utility functions.
  • libavfilter provides a mean to alter decoded Audio and Video through chain of filters.
  • libavdevice provides an abstraction to access capture and playback devices.
  • libswresample implements audio mixing and resampling routines.
  • libswscale implements color conversion and scaling routines.

Tools

  • ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
  • ffplay is a minimalistic multimedia player.
  • ffprobe is a simple analysis tool to inspect multimedia content.
  • Additional small tools such as aviocat, ismindex and qt-faststart.

Documentation

The offline documentation is available in the doc/ directory.

The online documentation is available in the main website and in the wiki.

Examples

Coding examples are available in the doc/examples directory.

License

FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.

Contributing

Patches should be submitted to the ffmpeg-devel mailing list using git format-patch or git send-email. Github pull requests should be avoided because they are not part of our review process and will be ignored.