[FFmpeg-trac] #8326(undetermined:new): signed integer overflow at libavformat/mpegenc.c:919

FFmpeg trac at avcodec.org
Tue Oct 22 10:54:03 EEST 2019

#8326: signed integer overflow at libavformat/mpegenc.c:919
             Reporter:  Suhwan       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  ubsan        |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Summary of the bug:
 There is a signed integer overflow at libavformat/mpegenc.c:919

 I compiled ffmpeg with "--toolchain=clang-usan" to check the undefined-
 behaviours and attached log file.

 I also ran this for 3mins to trigger this bug.

 How to reproduce:
 % ffmpeg_g -y -i $PoC -filter_complex rgbtestsrc -target svcd -loglevel 0
 -map 0 -psnr -c dirac -c:s:11 mpeg2video tmp.tedcaptions

 ffmpeg version N-95517-g0b8956b25c Copyright (c) 2000-2019 the FFmpeg
 built with clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
 configuration: --cc=clang --cxx=clang++ --ld=clang --enable-debug

 Here's UBSAN log

 libavformat/mpegenc.c:919:33: runtime error: signed integer overflow:
 -2147482382 - 2300 cannot be represented in type 'int'

 Thread 1 "ffmpeg_g" hit Breakpoint 1, 0x00000000004288b0 in
 __ubsan::ScopedReport::~ScopedReport() ()
 (gdb) bt
 #0  0x00000000004288b0 in __ubsan::ScopedReport::~ScopedReport() ()
 #1  0x000000000042b0eb in void
 handleIntegerOverflowImpl<__ubsan::Value>(__ubsan::OverflowData*, unsigned
 long, char const*, __ubsan::Value, __ubsan::ReportOptions) ()
 #2  0x000000000042c94f in __ubsan_handle_sub_overflow ()
 #3  0x00000000017936bc in flush_packet (ctx=<optimized out>,
 stream_index=<optimized out>,
     pts=<optimized out>, dts=<optimized out>, scr=<optimized out>,
     at libavformat/mpegenc.c:919
 #4  0x0000000001790c84 in output_packet (ctx=0x93cbd40, flush=0) at
 #5  0x000000000178d87a in mpeg_mux_write_packet (ctx=0x93cbd40,
 pkt=<optimized out>)
     at libavformat/mpegenc.c:1224
 #6  0x00000000017f5905 in write_packet (s=0x93cbd40, pkt=<optimized out>)
 at libavformat/mux.c:754
 #7  0x00000000017fc2c6 in av_interleaved_write_frame (s=<optimized out>,
     at libavformat/mux.c:1245
 #8  0x00000000004b5e0b in write_packet (of=<optimized out>,
 pkt=0x7fffffffc418, ost=<optimized out>,
     unqueue=<optimized out>) at fftools/ffmpeg.c:815
 #9  0x00000000004c58a6 in do_video_out (of=0x93ca0c0, ost=<optimized out>,
 next_picture=<optimized out>,
     sync_ipts=36766.000007629402) at fftools/ffmpeg.c:1321
 #10 0x00000000004c0f2b in reap_filters (flush=0) at fftools/ffmpeg.c:1504
 #11 0x000000000048c3d5 in transcode_from_filter (graph=0x93c7800,
 best_ist=<optimized out>)
     at fftools/ffmpeg.c:4533
 #12 transcode_step () at fftools/ffmpeg.c:4606
 #13 transcode () at fftools/ffmpeg.c:4682
 #14 0x0000000000487dc4 in main (argc=18, argv=<optimized out>) at
 (gdb) c
 Please confirm.

Ticket URL: <https://trac.ffmpeg.org/ticket/8326>
FFmpeg <https://ffmpeg.org>
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