Opened 8 days ago

Last modified 7 days ago

#7788 new defect

Custom-compiled FFmpeg 4.1.1 crashes on MacOS when reading files

Reported by: Jim_ChamSys Owned by:
Priority: normal Component: avcodec
Version: 4.1 Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

Hi there,

We bundle a version of FFmpeg with our software, in order to perform video transcoding. We compile this ourselves, to remove GPL-licensed code, and enable the VP9 codec.

Recently, we've upgraded our FFmpeg to version 4.1.1 (from 3.2.4); this has worked well on Windows and Linux platforms, but we're finding that our Mac version is segfaulting (signal 11) whenever it attempts to read certain video files. We don't have many different videos to test with, but it's been seen to crash with .wmv and .mpv files, but not with .mov files.

I've attached an archive that contains the binary executable and libraries we've built, the flags given to the configure script, and a test video that exhibits the issue.

The output when running FFmpeg through lldb is as follows:

$ lldb -- ffmpeg -i ~/Movies/Robotica_72011.mpv 
(lldb) target create "ffmpeg"
Current executable set to 'ffmpeg' (x86_64).
(lldb) settings set -- target.run-args  "-i" "/Users/buildbot/Movies/Robotica_72011.mpv"
(lldb) run
Process 91647 launched: '/usr/local/bin/ffmpeg' (x86_64)
ffmpeg version 4.1.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 8.1.0 (clang-802.0.38)
  configuration: --sysroot= --prefix=/usr/local/ --datadir=/usr/local/share/ffmpeg --enable-ffmpeg --disable-ffplay --disable-ffprobe --disable-doc --disable-network --enable-shared --disable-static --disable-gpl --disable-protocols --enable-protocol=data --enable-protocol=file --enable-protocol=pipe --enable-protocol=unix --enable-libvpx --disable-encoders --enable-encoder=pcm_s16le --enable-encoder=ljpeg --enable-encoder=mjpeg --enable-encoder=jpegls --enable-encoder=jpeg2000 --enable-encoder=png --enable-encoder=bmp --enable-encoder=libvpx_vp8 --enable-encoder=libvpx_vp9 --enable-decoder=png --enable-decoder=h264 --disable-bzlib --disable-lzma --enable-zlib --disable-openssl --disable-sdl2 --disable-securetransport --disable-libxcb --disable-devices --enable-lto --enable-pic --extra-ldflags='  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
Process 91647 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
    frame #0: 0x00000001009dbd72 libavcodec.58.dylib`ff_blockdsp_init + 134
libavcodec.58.dylib`ff_blockdsp_init:
->  0x1009dbd72 <+134>: movdqa %xmm0, (%rbx)
    0x1009dbd76 <+138>: andl   $0x8004000, %eax          ; imm = 0x8004000 
    0x1009dbd7b <+143>: cmpl   $0x4000, %eax             ; imm = 0x4000 
    0x1009dbd80 <+148>: jne    0x1009dbd9a               ; <+174>

As you can see, the only element of the backtrace is 'ff_blockdsp_init()'. We've reproduced this issue on three separate Mac computers (One running OSX 10.11, and two running OSX 10.13.6), and we've seen the exact same trace on all three, and with different video files.

Possibly related: In another part of the project, we're also making calls into libavcodec directly (in order to probe for video length, etc.), and we've been seeing similar Mac crashes on the same files; I suspect this is the same issue, although it doesn't happen reliably on all machines tested, and I've had a much harder time investigating it.

I'd be happy to provide more details if needed. Thanks for any assistance you can give.

Change History (7)

comment:1 Changed 8 days ago by Jim_ChamSys

I can't upload the archive because it's 20 MiB, so it's linked here: https://we.tl/t-ZDjzfTJGqF

comment:2 Changed 8 days ago by jamrial

  • Component changed from ffmpeg to avcodec

Can you compile ffmpeg with --enable-debug=gdb --disable-optimizations, and try to reproduce the crash again?
Also, post a backtrace and register state at the moment of the crash, not just the disassembly.

comment:3 Changed 8 days ago by Jim_ChamSys

I compiled with --enable-debug=gdb and --disable-optimizations (on top of the previously used flags), and the crash wouldn't happen:

$ lldb -- ffmpeg -i ~/Movies/Stormchasers_720.wmv
(lldb) target create "ffmpeg"
Current executable set to 'ffmpeg' (x86_64).
(lldb) settings set -- target.run-args  "-i" "/Users/buildbot/Movies/Stormchasers_720.wmv"
(lldb) run
Process 70612 launched: '/usr/local/bin/ffmpeg' (x86_64)
ffmpeg version 4.1.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 8.1.0 (clang-802.0.38)
  configuration: --sysroot= --prefix=/usr/local/ --datadir=/usr/local/share/ffmpeg --enable-ffmpeg --disable-ffplay --disable-ffprobe --disable-doc --disable-network --enable-shared --disable-static --disable-gpl --disable-protocols --enable-protocol=data --enable-protocol=file --enable-protocol=pipe --enable-protocol=unix --enable-libvpx --disable-encoders --enable-encoder=pcm_s16le --enable-encoder=ljpeg --enable-encoder=mjpeg --enable-encoder=jpegls --enable-encoder=jpeg2000 --enable-encoder=png --enable-encoder=bmp --enable-encoder=libvpx_vp8 --enable-encoder=libvpx_vp9 --enable-decoder=png --enable-decoder=h264 --disable-bzlib --disable-lzma --enable-zlib --disable-openssl --disable-sdl2 --disable-securetransport --disable-libxcb --disable-devices --enable-lto --enable-pic --extra-ldflags='  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
Input #0, asf, from '/Users/buildbot/Movies/Stormchasers_720.wmv':
  Metadata:
    WM/WMADRCAverageTarget: 8904
    WMFSDKNeeded    : 0.0.0.0000
    WM/WMADRCPeakReference: 31279
    WM/WMADRCPeakTarget: 31279
    WM/WMADRCAverageReference: 8904
    DeviceConformanceTemplate: MP@HL
    WMFSDKVersion   : 9.00.00.2980
    IsVBR           : 0
  Duration: 00:01:31.18, start: 0.000000, bitrate: 6331 kb/s
    Stream #0:0(eng): Audio: wmapro (b[1][0][0] / 0x0162), 48000 Hz, 5.1, fltp, 384 kb/s
    Stream #0:1(eng): Video: wmv3 (Main) (WMV3 / 0x33564D57), yuv420p, 1280x720, 6000 kb/s, 23.98 fps, 23.98 tbr, 1k tbn, 1k tbc
At least one output file must be specified

Since this seems to be optimisation-dependent, I tried again with only --enable-debug=gdb (and also getting the full backtrace, disassembly and registers like I should have done the first time):

$ lldb -- ffmpeg -i ~/Movies/Stormchasers_720.wmv
(lldb) target create "ffmpeg"
Current executable set to 'ffmpeg' (x86_64).
(lldb) settings set -- target.run-args  "-i" "/Users/buildbot/Movies/Stormchasers_720.wmv"
(lldb) run
Process 89551 launched: '/usr/local/bin/ffmpeg' (x86_64)
ffmpeg version 4.1.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 8.1.0 (clang-802.0.38)
  configuration: --sysroot= --prefix=/usr/local/ --datadir=/usr/local/share/ffmpeg --enable-ffmpeg --disable-ffplay --disable-ffprobe --disable-doc --disable-network --enable-shared --disable-static --disable-gpl --disable-protocols --enable-protocol=data --enable-protocol=file --enable-protocol=pipe --enable-protocol=unix --enable-libvpx --disable-encoders --enable-encoder=pcm_s16le --enable-encoder=ljpeg --enable-encoder=mjpeg --enable-encoder=jpegls --enable-encoder=jpeg2000 --enable-encoder=png --enable-encoder=bmp --enable-encoder=libvpx_vp8 --enable-encoder=libvpx_vp9 --enable-decoder=png --enable-decoder=h264 --disable-bzlib --disable-lzma --enable-zlib --disable-openssl --disable-sdl2 --disable-securetransport --disable-libxcb --disable-devices --enable-lto --enable-pic --extra-ldflags='  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
Process 89551 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
    frame #0: 0x00000001009dbd72 libavcodec.58.dylib`ff_blockdsp_init + 134
libavcodec.58.dylib`ff_blockdsp_init:
->  0x1009dbd72 <+134>: movdqa %xmm0, (%rbx)
    0x1009dbd76 <+138>: andl   $0x8004000, %eax          ; imm = 0x8004000 
    0x1009dbd7b <+143>: cmpl   $0x4000, %eax             ; imm = 0x4000 
    0x1009dbd80 <+148>: jne    0x1009dbd9a               ; <+174>
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
  * frame #0: 0x00000001009dbd72 libavcodec.58.dylib`ff_blockdsp_init + 134
    frame #1: 0x0000000100dd9ea3 libavcodec.58.dylib`ff_mpv_common_init + 695
    frame #2: 0x0000000100b0e3bb libavcodec.58.dylib`ff_h263_decode_init + 409
    frame #3: 0x0000000100e0dcf1 libavcodec.58.dylib`ff_msmpeg4_decode_init + 64
    frame #4: 0x0000000100f4da62 libavcodec.58.dylib`vc1_decode_init + 563
    frame #5: 0x0000000100f18937 libavcodec.58.dylib`avcodec_open2 + 3959
    frame #6: 0x00000001004f9e1c libavformat.58.dylib`avformat_find_stream_info + 748
    frame #7: 0x00000001000049a2 ffmpeg`open_input_file + 1682
    frame #8: 0x0000000100005dc8 ffmpeg`open_files + 248
    frame #9: 0x00000001000145ae ffmpeg`main + 2974
    frame #10: 0x00007fff5c060015 libdyld.dylib`start + 1
    frame #11: 0x00007fff5c060015 libdyld.dylib`start + 1
(lldb) reg read 
General Purpose Registers:
       rax = 0x00000000000fd3db
       rbx = 0x000000010302e8c8
       rcx = 0x0000000000000008
       rdx = 0x7fffffffffffffff
       rdi = 0x000000010302e8c8
       rsi = 0x00000000000002d0
       rbp = 0x0000000000000000
       rsp = 0x00007ffeefbfedd0
        r8 = 0x0000000000000000
        r9 = 0x0000000103012800
       r10 = 0x7fffffffffffffff
       r11 = 0x0000000000000003
       r12 = 0x0000000000000001
       r13 = 0x00000001028075c8
       r14 = 0x000000010302e160
       r15 = 0x000000010302de00
       rip = 0x00000001009dbd72  libavcodec.58.dylib`ff_blockdsp_init + 134
    rflags = 0x0000000000010202
        cs = 0x000000000000002b
        fs = 0x0000000000000000
        gs = 0x0000000000000000
(lldb) disass -s $pc-32 -e $pc+32
libavcodec.58.dylib`ff_blockdsp_init:
    0x1009dbd52 <+102>: wait   
    0x1009dbd53 <+103>: addb   %dh, %bl
    0x1009dbd55 <+105>: movd   %mm0, 0x9b456c(%rip)      ; (void *)0x00000001005dce70: ff_clear_block_sse
    0x1009dbd5c <+112>: jmp    0x1009dbd6e               ; <+130>
    0x1009dbd5e <+114>: movq   0x9b4572(%rip), %xmm1     ; (void *)0x00000001005dcec0: ff_clear_blocks_mmx, xmm1 = mem[0],zero 
    0x1009dbd66 <+122>: movq   0x9b4552(%rip), %xmm0     ; (void *)0x00000001005dce20: ff_clear_block_mmx, xmm0 = mem[0],zero 
    0x1009dbd6e <+130>: punpcklqdq %xmm1, %xmm0              ; xmm0 = xmm0[0],xmm1[0] 
->  0x1009dbd72 <+134>: movdqa %xmm0, (%rbx)
    0x1009dbd76 <+138>: andl   $0x8004000, %eax          ; imm = 0x8004000 
    0x1009dbd7b <+143>: cmpl   $0x4000, %eax             ; imm = 0x4000 
    0x1009dbd80 <+148>: jne    0x1009dbd9a               ; <+174>
    0x1009dbd82 <+150>: movq   0x9b4546(%rip), %xmm0     ; (void *)0x00000001005dcf40: ff_clear_blocks_avx, xmm0 = mem[0],zero 
    0x1009dbd8a <+158>: movq   0x9b4526(%rip), %xmm1     ; (void *)0x00000001005dcea0: ff_clear_block_avx, xmm1 = mem[0],zero 

comment:4 Changed 8 days ago by jamrial

I compiled with --enable-debug=gdb and --disable-optimizations (on top of the previously used flags), and the crash wouldn't happen

rbx = 0x000000010302e8c8
-> 0x1009dbd72 <+134>: movdqa %xmm0, (%rbx)

Looks like a compiler bug. The code it generates results in unaligned memory access when using movdqa, something that doesn't happen when you compile with --disable-optimizations as it removes -O3 and similar compiler optimization flags.

Is this the same compiler you used for ffmpeg 3.4.2, which you say worked? It's evidently ignoring the -fno-tree-vectorize flag we use precisely to prevent compilers from making mistakes like this.

comment:5 Changed 8 days ago by Jim_ChamSys

I'm afraid there's been a fair amount of juggling with SDKs lately, so I'm not 100% certain that the exact same compiler is being used; however, both the new and previous versions of FFmpeg report that they were compiled with "Apple LLVM version 8.1.0 (clang-802.0.38)". We're now using SDK version 10.11, in any case.

Also, I'm afraid I made a mistake in my first post; the original FFmpeg version used was 3.3.1 on the Mac (it was 3.2.4 on the other platforms).

comment:6 Changed 8 days ago by jamrial

Can you try configuring with --extra-cflags="-fno-slp-vectorize" and see if that fixes the crash when you don't use --disable-optimizations?

comment:7 Changed 7 days ago by Jim_ChamSys

I've tried "--extra-cflags="-fno-slp-vectorize""; it still crashes. It looks like the same issue (same backtrace and disassembly address, at least) but I can provide the full logs if you want.

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