[Bug 2112466] Re: /usr/share/apport/apport:FileNotFoundError:/usr/share/apport/apport at 600:get_pid_info on /proc/<pid>

[Benjamin Drung]

I can reproduce this issue by executing this in the terminal on Ubuntu
22.04:

```
$ sleep 3600 &
[1] 40965
$ pid=40965
$ kill -11 $pid && sleep 0.02 && kill -9 $pid
```

The second sleep needs to be adjusted to be between the kernel calling
Apport and Apport starting.

An alternative explanation would be that there might be environments
where /proc is not mounted. Should we cover this case? Check for /proc
and mount it if it is missing? Or should we do nothing and exit
gracefully?

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https://bugs.launchpad.net/bugs/2112466

Title:
  /usr/share/apport/apport:FileNotFoundError:/usr/share/apport/apport at 600:get_pid_info
  on /proc/<pid>

Status in apport package in Ubuntu:
  Fix Released
Status in apport source package in Jammy:
  New

Bug description:
  [Original Report]

  ```
  Traceback (most recent call last):
    File "/usr/share/apport/apport", line 600, in <module>
      get_pid_info(pid)
    File "/usr/share/apport/apport", line 97, in get_pid_info
      proc_pid_fd = os.open('/proc/%s' % pid, os.O_RDONLY | os.O_PATH | os.O_DIRECTORY)
  FileNotFoundError: [Errno 2] No such file or directory: '/proc/10754'
  ```

  The Ubuntu Error Tracker has been receiving reports about a problem regarding apport.  This problem was most recently seen with package version 2.20.11-0ubuntu82.7, the problem page at https://errors.ubuntu.com/problem/43f924069e9e0d6cdb25ce58213a1f3dfa6e966e contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
  If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.

  [ Impact ]

   * This is #2 on https://errors.ubuntu.com/?package=apport&period=day

   * Print a proper error message if /proc/<pid> is gone instead of the
  current error:

   ```
   Traceback (most recent call last):
     File "/usr/share/apport/apport", line 600, in <module>
       get_pid_info(pid)
     File "/usr/share/apport/apport", line 97, in get_pid_info
       proc_pid_fd = os.open('/proc/%s' % pid, os.O_RDONLY | os.O_PATH | os.O_DIRECTORY)
   FileNotFoundError: [Errno 2] No such file or directory: '/proc/10754'
   ```

   * The upload fixes the bug as
  https://github.com/canonical/apport/commit/fcbb93816aa367f2bd35c029ca8ecc0d83992722
  introduced proper error logging for this exception

  [ Test Plan ]

   * This crash can be reproduced by testing with a fake pid or killing
  a pid being tracked by apport:

  ```
  FAKE_PID=2147483647

  if [ -e "/proc/$FAKE_PID" ]; then
      echo "Error: /proc/$FAKE_PID exists"
      exit 1
  fi

  apport -p FAKE_PID
  ```

  If we get an error, we can retry after applying the patch and we
  should get a proper error message.

   * Commit fcbb93816aa367f2bd35c029ca8ecc0d83992722 also introduced a
  unit test for this bug fix so that it can be tested with a fake pid

  [ Where problems could occur ]

   * The only code change is a try catch exception for this case and a
  unit test, one of the sources of problems could be a possible syntax
  error which leads to an ftbfs for apport

   * Since apport is primarily for crash reports, user experience is
  unlikely to be affected much

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