[FFmpeg-trac] #4587(avcodec:new): ouf-of-boundry memory access in cabac(H264)

[FFmpeg]

#4587: ouf-of-boundry memory access in cabac(H264)
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             Reporter:  rakexue  |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  avcodec  |                  Version:  unspecified
             Keywords:  H264     |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
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 The specific h264 file decoding causes some random SIGBUS on arm Android.

 CallStack shows the crash in get_cabac_inline(ARM).

 Turn off UNCHECKED_BITSTREAM_READER, then find that
 get_cabac_inline(plain C ) -> refill2 occasionally accesses the last two
 bytes just after the boundry(CABACContext.bytestream_end[0] and
 CABACContext.bytestream_end[1]).

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Ticket URL: <https://trac.ffmpeg.org/ticket/4587>
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