[FFmpeg-trac] #9099(avcodec:new): FFmpeg/libavcodec: NULL Pointer Dereference

FFmpeg trac at avcodec.org
Wed Feb 10 17:09:20 EET 2021


#9099: FFmpeg/libavcodec: NULL Pointer Dereference
-------------------------------------+-------------------------------------
             Reporter:  QiuhaoLi     |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:  avcodec      |                  Version:  git-
             Keywords:  NULL         |  master
  Pointer Dereference                |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 -- [ Description

 During fuzzing, we found a null pointer dereference (CWE-476) in the
 latest FFmpeg/libavcodec.

 I sent a report to ffmpeg-security at ffmpeg.org, but didn't get a reply yet.

 -- [ Affected Version

 ubuntu at VM-0-6-ubuntu:~/ffmpeg_sources/FFmpeg$ git log | head -n 4
 commit 129978af6b6503109517777eba8890713a787cb5
 Author: Paul B Mahol <onemda at gmail.com>
 Date:   Wed Feb 10 14:08:23 2021 +0100


 -- [ Reproduce with ASAN & Report

 ubuntu at VM-0-6-ubuntu:~$ FFREPORT=1 ./bin/ffmpeg -i PoC output.mp4 # sorry
 I didn't go deep to figure out the format of the PoC
 Report written to "ffmpeg-20210210-224350.log"
 Log level: 48
 ffmpeg version N-101043-g129978af6b Copyright (c) 2000-2021 the FFmpeg
 developers
   built with clang version 10.0.0-4ubuntu1
   configuration: --prefix=/home/ubuntu/ffmpeg_build --pkg-config-
 flags=--static --extra-cflags='-I/home/ubuntu/ffmpeg_build/include -ggdb
 -fsanitize=address -fsanitize=undefined' --extra-
 ldflags='-L/home/ubuntu/ffmpeg_build/lib -fsanitize=address
 -fsanitize=undefined' --extra-libs='-lpthread -lm'
 --bindir=/home/ubuntu/bin --cc=clang --cxx=clang++ --disable-ffplay
 --disable-ffprobe --disable-stripping --assert-level=2 --enable-gpl
 --enable-gnutls --enable-libaom --enable-libass --enable-libfdk-aac
 --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-
 libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-
 nonfree
   libavutil      56. 65.100 / 56. 65.100
   libavcodec     58.122.100 / 58.122.100
   libavformat    58. 67.100 / 58. 67.100
   libavdevice    58. 11.103 / 58. 11.103
   libavfilter     7.103.100 /  7.103.100
   libswscale      5.  8.100 /  5.  8.100
   libswresample   3.  8.100 /  3.  8.100
   libpostproc    55.  8.100 / 55.  8.100
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] overread end of atom 'stsd' by
 808464282 bytes
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] stream 0, timescale not set
 [hevc @ 0x619000000f80] Invalid NAL unit size in extradata.
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Failed to open codec in
 avformat_find_stream_info
 [hevc @ 0x619000000f80] Invalid NAL unit size in extradata.
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Failed to open codec in
 avformat_find_stream_info
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Could not find codec parameters
 for stream 0 (Video: hevc (Hvc1 / 0x31637648), none, 12336x12336):
 unspecified pixel format
 Consider increasing the value for the 'analyzeduration' (0) and
 'probesize' (5000000) options
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'PoC':
   Duration: N/A, bitrate: N/A
   Stream #0:0: Video: hevc (Hvc1 / 0x31637648), none, 12336x12336, 1 tbr,
 1 tbn, 1 tbc
     Metadata:
       handler_name    : 0000000000000
       vendor_id       : 0000
       encoder         : 0000000000000000000000000000000
 [hevc @ 0x619000002d80] Invalid NAL unit size in extradata.
 libavcodec/hevcdec.c:3427:22: runtime error: applying zero offset to null
 pointer
 SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
 libavcodec/hevcdec.c:3427:22 in
 libavcodec/hevcdec.c:3427:22: runtime error: load of null pointer of type
 'HEVCLocalContext *' (aka 'struct HEVCLocalContext *')
 SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
 libavcodec/hevcdec.c:3427:22 in
 AddressSanitizer:DEADLYSIGNAL
 =================================================================
 ==23809==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000
 (pc 0x0000035bf9ad bp 0x0c4c00001224 sp 0x7ffef55e8e20 T0)
 ==23809==The signal is caused by a READ memory access.
 ==23809==Hint: address points to the zero page.
     #0 0x35bf9ad in hevc_decode_free
 /home/ubuntu/ffmpeg_sources/FFmpeg/libavcodec/hevcdec.c:3427:19
     #1 0x4688cde in ff_frame_thread_free
 /home/ubuntu/ffmpeg_sources/FFmpeg/libavcodec/pthread_frame.c:712:13
     #2 0x468d646 in ff_frame_thread_init
 /home/ubuntu/ffmpeg_sources/FFmpeg/libavcodec/pthread_frame.c:885:5
     #3 0x4e0ffa8 in avcodec_open2
 /home/ubuntu/ffmpeg_sources/FFmpeg/libavcodec/utils.c:759:15
     #4 0x57c0c4 in init_input_stream
 /home/ubuntu/ffmpeg_sources/FFmpeg/fftools/ffmpeg.c:2988:20
     #5 0x57c0c4 in transcode_init
 /home/ubuntu/ffmpeg_sources/FFmpeg/fftools/ffmpeg.c:3751:20
     #6 0x56f0d7 in transcode
 /home/ubuntu/ffmpeg_sources/FFmpeg/fftools/ffmpeg.c:4752:11
     #7 0x56c7b2 in main
 /home/ubuntu/ffmpeg_sources/FFmpeg/fftools/ffmpeg.c:4986:9
     #8 0x7fe2dcb100b2 in __libc_start_main /build/glibc-
 eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
     #9 0x4251ad in _start (/home/ubuntu/bin/ffmpeg+0x4251ad)

 AddressSanitizer can not provide additional info.
 SUMMARY: AddressSanitizer: SEGV
 /home/ubuntu/ffmpeg_sources/FFmpeg/libavcodec/hevcdec.c:3427:19 in
 hevc_decode_free
 ==23809==ABORTING

 ubuntu at VM-0-6-ubuntu:~$ cat ffmpeg-20210210-224350.log
 ffmpeg started on 2021-02-10 at 22:43:50
 Report written to "ffmpeg-20210210-224350.log"
 Log level: 48
 Command line:
 ./bin/ffmpeg -i PoC output.mp4
 ffmpeg version N-101043-g129978af6b Copyright (c) 2000-2021 the FFmpeg
 developers
   built with clang version 10.0.0-4ubuntu1
   configuration: --prefix=/home/ubuntu/ffmpeg_build --pkg-config-
 flags=--static --extra-cflags='-I/home/ubuntu/ffmpeg_build/include -ggdb
 -fsanitize=address -fsanitize=undefined' --extra-
 ldflags='-L/home/ubuntu/ffmpeg_build/lib -fsanitize=address
 -fsanitize=undefined' --extra-libs='-lpthread -lm'
 --bindir=/home/ubuntu/bin --cc=clang --cxx=clang++ --disable-ffplay
 --disable-ffprobe --disable-stripping --assert-level=2 --enable-gpl
 --enable-gnutls --enable-libaom --enable-libass --enable-libfdk-aac
 --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-
 libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-
 nonfree
   libavutil      56. 65.100 / 56. 65.100
   libavcodec     58.122.100 / 58.122.100
   libavformat    58. 67.100 / 58. 67.100
   libavdevice    58. 11.103 / 58. 11.103
   libavfilter     7.103.100 /  7.103.100
   libswscale      5.  8.100 /  5.  8.100
   libswresample   3.  8.100 /  3.  8.100
   libpostproc    55.  8.100 / 55.  8.100
 Splitting the commandline.
 Reading option '-i' ... matched as input url with argument 'PoC'.
 Reading option 'output.mp4' ... matched as output url.
 Finished splitting the commandline.
 Parsing a group of options: global .
 Successfully parsed a group of options.
 Parsing a group of options: input url PoC.
 Successfully parsed a group of options.
 Opening an input file: PoC.
 [NULL @ 0x61b000000080] Opening 'PoC' for reading
 [file @ 0x610000000040] Setting default whitelist 'file,crypto,data'
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Format mov,mp4,m4a,3gp,3g2,mj2
 probed with size=2048 and score=100
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] overread end of atom 'stsd' by
 808464282 bytes
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] stream 0, timescale not set
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Before
 avformat_find_stream_info() pos: 495 bytes read:495 seeks:2 nb_streams:1
 [hevc @ 0x619000000f80] Invalid NAL unit size in extradata.
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Failed to open codec in
 avformat_find_stream_info
 [hevc @ 0x619000000f80] Invalid NAL unit size in extradata.
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Failed to open codec in
 avformat_find_stream_info
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] Could not find codec parameters
 for stream 0 (Video: hevc (Hvc1 / 0x31637648), none, 12336x12336):
 unspecified pixel format
 Consider increasing the value for the 'analyzeduration' (0) and
 'probesize' (5000000) options
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x61b000000080] After
 avformat_find_stream_info() pos: 495 bytes read:495 seeks:2 frames:0
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'PoC':
   Duration: N/A, bitrate: N/A
   Stream #0:0, 0, 1/1: Video: hevc (Hvc1 / 0x31637648), none, 12336x12336,
 1 tbr, 1 tbn, 1 tbc
     Metadata:
       handler_name    : 0000000000000
       vendor_id       : 0000
       encoder         : 0000000000000000000000000000000
 Successfully opened the file.
 Parsing a group of options: output url output.mp4.
 Successfully parsed a group of options.
 Opening an output file: output.mp4.
 [file @ 0x610000001640] Setting default whitelist 'file,crypto,data'
 Successfully opened the file.
 detected 16 logical cores
 [hevc @ 0x619000002d80] Invalid NAL unit size in extradata.


 -- [ GDB Report

 ubuntu at VM-0-6-ubuntu:~$ gdb --args ./bin/ffmpeg -i PoC output.mp4
 (gdb) run
 (gdb) bt
 #0  0x00000000035bf9ad in hevc_decode_free (avctx=<optimized out>) at
 libavcodec/hevcdec.c:3427
 #1  0x0000000004688cdf in ff_frame_thread_free (avctx=0x619000001480,
 thread_count=<optimized out>) at libavcodec/pthread_frame.c:712
 #2  0x000000000468d647 in ff_frame_thread_init (avctx=<optimized out>) at
 libavcodec/pthread_frame.c:885
 #3  0x00000000070a9b23 in ff_thread_init (avctx=<optimized out>) at
 libavcodec/pthread.c:77
 #4  0x0000000004e0ffa9 in avcodec_open2 (avctx=<optimized out>,
 codec=0x9aa5ec0 <ff_hevc_decoder>, options=<optimized out>) at
 libavcodec/utils.c:759
 #5  0x000000000057c0c5 in init_input_stream (ist_index=<optimized out>,
 error=0x7fffffffc660 "", error_len=1024) at fftools/ffmpeg.c:2988
 #6  transcode_init () at fftools/ffmpeg.c:3751
 #7  0x000000000056f0d8 in transcode () at fftools/ffmpeg.c:4752
 #8  0x000000000056c7b3 in main (argc=<optimized out>, argv=<optimized
 out>) at fftools/ffmpeg.c:4986

 (gdb) disass $pc-32,$pc+32
 Dump of assembler code from 0x35bf98d to 0x35bf9cd:
    0x00000000035bf98d <hevc_decode_free+1317>:  add    (%rax),%al
    0x00000000035bf98f <hevc_decode_free+1319>:  add    %cl,-0x7b(%rax)
    0x00000000035bf992 <hevc_decode_free+1322>:  fisttpl (%rdi)
    0x00000000035bf994 <hevc_decode_free+1324>:  test   %ah,(%rbx)
    0x00000000035bf996 <hevc_decode_free+1326>:  add    (%rax),%al
    0x00000000035bf998 <hevc_decode_free+1328>:  add    %cl,-0x77(%rax)
    0x00000000035bf99b <hevc_decode_free+1331>:  fmuls  -0x3f(%rax)
    0x00000000035bf99e <hevc_decode_free+1334>:  callq  0x41479a6
 <skip_bits_long+742>
    0x00000000035bf9a3 <hevc_decode_free+1339>:  cmp    $0x7f,%bh
    0x00000000035bf9a6 <hevc_decode_free+1342>:  add    %cl,(%rdi)
    0x00000000035bf9a8 <hevc_decode_free+1344>:  test   %ebp,(%rdx)
    0x00000000035bf9aa <hevc_decode_free+1346>:  add    (%rax),%eax
    0x00000000035bf9ac <hevc_decode_free+1348>:  add
 %cl,0x23(%rbx,%rdi,1)
    0x00000000035bf9b0 <hevc_decode_free+1352>:  mov    0x8(%rsp),%r12
    0x00000000035bf9b5 <hevc_decode_free+1357>:  jne    0x35bf9de
 <hevc_decode_free+1398>
    0x00000000035bf9b7 <hevc_decode_free+1359>:  test   %r14b,%r14b
    0x00000000035bf9ba <hevc_decode_free+1362>:  je     0x35bfc69
 <hevc_decode_free+2049>
    0x00000000035bf9c0 <hevc_decode_free+1368>:  test   $0x7,%r15b
    0x00000000035bf9c4 <hevc_decode_free+1372>:  jne    0x35bfc7f
 <hevc_decode_free+2071>
    0x00000000035bf9ca <hevc_decode_free+1378>:  cmpb
 $0x0,0x7fff8000(%rbp)
 End of assembler dump.

 (gdb) info all-registers
 rax            0x0                 0
 rbx            0x0                 0
 rcx            0x0                 0
 rdx            0xc4c00001223       13520557052451
 rsi            0x0                 0
 rdi            0x7fffffffb6a9      140737488336553
 rbp            0xc4c00001224       0xc4c00001224
 rsp            0x7fffffffb780      0x7fffffffb780
 r8             0x7fffffffaa70      140737488333424
 r9             0x2                 2
 r10            0x7e98b73           132746099
 r11            0x206               518
 r12            0x0                 0
 r13            0x626000009118      108164456419608
 r14            0x624000002101      108027017437441
 r15            0x626000009120      108164456419616
 rip            0x35bf9ad           0x35bf9ad <hevc_decode_free+1349>
 eflags         0x10246             [ PF ZF IF RF ]
 cs             0x33                51
 ss             0x2b                43
 ds             0x0                 0
 es             0x0                 0
 fs             0x0                 0
 gs             0x0                 0
 st0            0                   (raw 0x00000000000000000000)
 st1            0                   (raw 0x00000000000000000000)
 st2            0                   (raw 0x00000000000000000000)
 st3            0                   (raw 0x00000000000000000000)
 st4            0                   (raw 0x00000000000000000000)
 st5            0                   (raw 0x00000000000000000000)
 st6            0                   (raw 0x00000000000000000000)
 st7            0                   (raw 0x00000000000000000000)
 fctrl          0x37f               895
 fstat          0x0                 0
 ftag           0xffff              65535
 fiseg          0x0                 0
 fioff          0x0                 0
 foseg          0x0                 0
 fooff          0x0                 0
 fop            0x0                 0
 mxcsr          0x1fa0              [ PE IM DM ZM OM UM PM ]
 bndcfgu        {raw = 0x0, config = {base = 0x0, reserved = 0x0, preserved
 = 0x0, enabled = 0x0}} {raw = 0x0, config = {base = 0, reserved = 0,
 preserved = 0, enabled = 0}}
 bndstatus      {raw = 0x0, status = {bde = 0x0, error = 0x0}} {raw = 0x0,
 status = {bde = 0, error = 0}}
 k0             0x0                 0
 k1             0x0                 0
 k2             0x0                 0
 k3             0x0                 0
 k4             0x0                 0
 k5             0x0                 0
 k6             0x0                 0
 k7             0x0                 0
 /* ... */


 -- [ PoC base64 encoded

 ubuntu at VM-0-6-ubuntu:~$ base64 PoC
 MDAwMG1vb3YAAABsMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAw
 MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAw
 MDAwMDAwdHJhawAAAFwwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAw
 MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwAAAAHDAwMDAwMDAw
 MDAwMDAwMDAwMDAwMDAwMAAAAC1oZGxyMDAwMDAwMDB2aWRlMDAwMDAwMDAwMDAwMDAwMDAwMDAw
 MDAwMAAAAAEwMDAwAAAAAAAAABwwMDAwMDAwMDAwMDAAAAAMMDAwMDAwMDAwMDAwc3RzZDAwMDAA
 AAABMDAwMGVuY3YwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAw
 MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAAAAA0YXZjQzAwMDAwMDAwMDAwMDAwMDAw
 MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMGZybWFIdmMx


 Thank you.
   Qiuhao Li

--
Ticket URL: <https://trac.ffmpeg.org/ticket/9099>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker


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