Opened 2 months ago

Last modified 2 months ago

#9099 closed defect

FFmpeg/libavcodec: NULL Pointer Dereference — at Initial Version

Reported by: QiuhaoLi Owned by:
Priority: important Component: avcodec
Version: git-master Keywords: hevc crash SIGSEGV regression
Cc: Blocked By:
Blocking: Reproduced by developer: yes
Analyzed by developer: no

Description

-- [ Description

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

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

-- [ Affected Version

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

-- [ Reproduce with ASAN & Report

ubuntu@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@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@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@VM-0-6-ubuntu:~$ base64 PoC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Thank you.

Qiuhao Li

Change History (1)

Changed 2 months ago by QiuhaoLi

The crash input file (SEGV: Read on address 0x000000000000)

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