New subject: #9844(avdevice:closed): Memory leak in v4l2 input device if setting timestamps option to mono2abs or abs

25 Jul 2022

      #9844: Memory leak in v4l2 input device if setting timestamps option to mono2abs
or abs
-------------------------------------+-------------------------------------
             Reporter:  bermond      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avdevice     |                  Version:  git-
             Keywords:  v4l2         |  master
  video4linux2 leak                  |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 ASan reports a memory leak when closing a `'v4l2'` input device if the
 `'timestamps'` option is setted to `'mono2abs'` or `'abs'`. These values
 converts of the start timestamp.

 Using the value `'default'` (which does not convert start timestamp) does
 not cause a memory leak.

 How to reproduce:
 {{{#!c
 #include <stdio.h>
 #include <libavdevice/avdevice.h>
 #include <libavformat/avformat.h>
 #include <libavcodec/avcodec.h>
 #include <libavutil/avutil.h>

 int main() {
     int ret;
     AVDictionary* inputOptions = NULL;

     // "mono2abs" and "abs" causes a memory leak ("default" does not leak)
     ret = av_dict_set(&inputOptions, "timestamps", "mono2abs", 0);
     if (ret < 0) {
         fprintf(stderr, "Failed to set v4l2 'timestamp' option");
         goto end;
     }

     avdevice_register_all();

     const AVInputFormat* inputFormat = av_find_input_format("v4l2");
     if (!inputFormat) {
         fprintf(stderr, "Failed to find input format");
         ret = -1;
         goto end;
     }

     AVFormatContext* inputFormatContext = avformat_alloc_context();
     if (!inputFormatContext) {
         fprintf(stderr, "Failed to allocate input format context");
         ret = AVERROR(ENOMEM);
         goto end;
     }

     ret = avformat_open_input(&inputFormatContext, "/dev/video0",
 inputFormat, &inputOptions);
     if (ret < 0) {
         fprintf(stderr, "Failed to open input device");
         goto end;
     }

     ret = avformat_find_stream_info(inputFormatContext, NULL);
     if (ret < 0) {
         fprintf(stderr, "Failed to find input stream info");
         goto end;
     }

     av_dump_format(inputFormatContext, 0, "/dev/video0", 0);

     AVPacket* inputPacket = av_packet_alloc();
     if (!inputPacket) {
         fprintf(stderr, "Failed to allocate input packet");
         ret = AVERROR(ENOMEM);
         goto end;
     }

     // read at least one frame to avoid this error on closing:
 "ioctl(VIDIOC_QBUF): Bad file descriptor"
     ret = av_read_frame(inputFormatContext, inputPacket);
     if (ret < 0) {
         fprintf(stderr, "Failed to read input packet");
         goto end;
     }

     ret = 0;

 end:
     av_dict_free(&inputOptions);
     av_packet_free(&inputPacket);
     avformat_close_input(&inputFormatContext);

     return ret;
 }
 }}}

 Compiled with:
 {{{
 $ gcc v4l2_mem_leak.c -o v4l2_mem_leak -g -Wall -Wextra -pedantic
 -fsanitize=address -fno-omit-frame-pointer -lavdevice -lavformat -lavutil
 -lavcodec
 }}}

 Output:
 {{{
 $ ./v4l2_mem_leak
 [video4linux2,v4l2 @ 0x617000002000] Detected monotonic timestamps,
 converting
 Input #0, video4linux2,v4l2, from '/dev/video0':
   Duration: N/A, start: 1658787218.575150, bitrate: 110592 kb/s
   Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480,
 110592 kb/s, 30 fps, 30 tbr, 1000k tbn

 =================================================================
 ==5506==ERROR: LeakSanitizer: detected memory leaks

 Direct leak of 40 byte(s) in 1 object(s) allocated from:
     #0 0x7f90b0ebefc7 in __interceptor_posix_memalign
 /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:145
     #1 0x7f90b064fdb5 in av_malloc (/usr/lib/libavutil.so.57+0x4fdb5)

 SUMMARY: AddressSanitizer: 40 byte(s) leaked in 1 allocation(s).
 }}}

 Compiler is gcc 12.1.0.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9844>
FFmpeg <https://ffmpeg.org>
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#9844(avdevice:new): Memory leak in v4l2 input device if setting timestamps option to mono2abs or abs

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