> 2021年12月3日 下午5:45，Andreas Rheinhardt <andreas.rheinha...@outlook.com> 写道：
>
> Yu Yang:
>> 'pkt' and '*pkt' should be judged separately for release.
>> SEGV by a READ memory access (address points to the zero page)
>>
>> ```c
>> // in fftools/ffmpeg.c:515
>> 515 static void ffmpeg_cleanup(int ret)
>> 516 {
>> ...
>>
>> 626 for (i = 0; i < nb_input_files; i++) {
>> 627 avformat_close_input(&input_files[i]->ctx);
>> // `input_files[0] == NULL` but `&input_files[0]->pkt == 0x68`,
>> see below;
>> 628 av_packet_free(&input_files[i]->pkt);
>> 629 av_freep(&input_files[i]);
>> 630 }
>>
>> ...
>> 674 }
>> ```
>> ```c
>> // in libavcodec/avpacket.c:75
>> 75 void av_packet_free(AVPacket **pkt)
>> 76 {
>> // pkt == 0x68, `*pkt` cause `SEGV`.
>> 77 if (!pkt || !*pkt)
>> 78 return;
>> 79
>> 80 av_packet_unref(*pkt);
>> 81 av_freep(pkt);
>> 82 }
>> ```
>>
>> coredump backtrace info:
>> ==4536==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000068 (pc
>> 0x000002a794d0 bp 0x7ffdf587a910 sp 0x7ffdf587a8e0 T0)
>> ==4536==The signal is caused by a READ memory access.
>> ==4536==Hint: address points to the zero page.
>> #0 0x2a794d0 in av_packet_free
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavcodec/avpacket.c:77:18
>> #1 0x592107 in ffmpeg_cleanup
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:628:9
>> #2 0x55fe0e in exit_program
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/cmdutils.c:136:9
>> #3 0x4cfcd4 in open_input_file
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg_opt.c:1268:9
>> exit_program
>> #4 0x4c9dc0 in open_files
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg_opt.c:3338:15
>> #5 0x4c9295 in ffmpeg_parse_options
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg_opt.c:3378:11 open_file
>> #6 0x58f241 in main
>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4988:11
>> #7 0x7f122a83d0b2 in __libc_start_main
>> /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
>> #8 0x42033d in _start (/home/r1/ffmpeg/ffmpeg_4.4.1+0x42033d)
>>
>>
>> Reported-by: TOTE Robot <os...@tsinghua.edu.cn>
>> Signed-off-by: Yu Yang <young_chel...@163.com>
>> ---
>> libavcodec/avpacket.c | 9 ++++-----
>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
>> index d8d8fef3b9..8348bec581 100644
>> --- a/libavcodec/avpacket.c
>> +++ b/libavcodec/avpacket.c
>> @@ -74,11 +74,10 @@ AVPacket *av_packet_alloc(void)
>>
>> void av_packet_free(AVPacket **pkt)
>> {
>> - if (!pkt || !*pkt)
>> - return;
>> -
>> - av_packet_unref(*pkt);
>> - av_freep(pkt);
>> + if (*pkt)
>> + av_packet_unref(*pkt);
>> + if (pkt)
>> + av_freep(pkt);
>> }
>>
>> static int packet_alloc(AVBufferRef **buf, int size)
>>
>
> This change makes no sense at all: If pkt == NULL (this should actually
> never happen and indicates a bug somewhere else; we should actually not
> check for this, but legacy), then the first check dereferences a NULL
> pointer and crashes.
Thx, the code I wrote is indeed too stupid.
>
> - Andreas
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
