[Bug 2037595] Re: _gpgme_io_select breaks when more than 1024 file descriptors are open

Wed Mar 6 04:21:40 UTC 2024

ubuntu at sru-jammy:~$ python3
Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import gpg
>>> c = gpg.Context()
>>> list(c.keylist())
[]
>>> fs = []
>>> for i in range(1024):
...     fs.append(open('/dev/null'))
...
>>> list(c.keylist())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/gpg/core.py", line 762, in keylist
    key = self.op_keylist_next()
  File "/usr/lib/python3/dist-packages/gpg/core.py", line 1206, in op_keylist_next
    raise excp
  File "/usr/lib/python3/dist-packages/gpg/core.py", line 1201, in op_keylist_next
    errorcheck(gpgme.gpgme_op_keylist_next(self.wrapped, ptr))
  File "/usr/lib/python3/dist-packages/gpg/errors.py", line 129, in errorcheck
    raise GPGMEError(retval, extradata)
gpg.errors.GPGMEError: GPGME: Too many open files
>>>
ubuntu at sru-jammy:~$ sudo apt install -t jammy-proposed libgpgme11
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages will be upgraded:
  libgpgme11
1 upgraded, 0 newly installed, 0 to remove and 32 not upgraded.
Need to get 136 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 libgpgme11 amd64 1.16.0-1.2ubuntu4.2 [136 kB]
Fetched 136 kB in 1s (104 kB/s)
(Reading database ... 34017 files and directories currently installed.)
Preparing to unpack .../libgpgme11_1.16.0-1.2ubuntu4.2_amd64.deb ...
Unpacking libgpgme11:amd64 (1.16.0-1.2ubuntu4.2) over (1.16.0-1.2ubuntu4.1) ...
Setting up libgpgme11:amd64 (1.16.0-1.2ubuntu4.2) ...
Processing triggers for libc-bin (2.35-0ubuntu3.6) ...
Scanning processes...

No services need to be restarted.

No containers need to be restarted.

No user sessions are running outdated binaries.

No VM guests are running outdated hypervisor (qemu) binaries on this host.
ubuntu at sru-jammy:~$ python3
Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import gpg
>>> c = gpg.Context()
>>> list(c.keylist())
[]
>>> fs = []
>>> for i in range(1024)
  File "<stdin>", line 1
    for i in range(1024)
                        ^
SyntaxError: expected ':'
>>> for i in range(1024):
...     fs.append(open('/dev/null'))
...
>>> list(c.keylist())
[]
>>>

** Tags removed: verification-needed-jammy
** Tags added: verification-done-jammy

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https://bugs.launchpad.net/bugs/2037595

Title:
  _gpgme_io_select breaks when more than 1024 file descriptors are open

Status in gpgme1.0 package in Ubuntu:
  Fix Released
Status in gpgme1.0 source package in Focal:
  Fix Committed
Status in gpgme1.0 source package in Jammy:
  Fix Committed

Bug description:
  [Impact]

  Launchpad's buildd-manager is a complex event-driven daemon that
  manages several hundred builders on production.  As such, it can often
  end up with more than 1024 file descriptors open.  It also uses gpgme
  from time to time to fetch signing keys for PPAs when dispatching
  builds that involve PPAs.

  On focal (and also on jammy), this breaks because `_gpgme_io_select`
  is implemented using select(2), whose manual page says: "WARNING:
  select() can monitor only file descriptors numbers that are less than
  FD_SETSIZE (1024)—an unreasonably low limit for many modern
  applications—and this limitation will not change.  All modern
  applications should instead use poll(2) or epoll(7), which do not
  suffer this limitation."  This is exactly the limitation we're running
  into, resulting in mysterious "Too many open files" errors despite
  resource limits being set to more than comfortable values.

  Fortunately, this was fixed upstream in https://git.gnupg.org/cgi-
  bin/gitweb.cgi?p=gpgme.git;a=commitdiff;h=8148237cb4ae20755c06a44d71761c7030973c3d,
  and lunar has that fix.  focal and jammy do not (there may be a
  similar problem with older LTSes too, but I only care about it back to
  focal).  buildd-manager currently runs on focal.

  We've been running buildd-manager with a cherry-picked fix from
  upstream for a few weeks now, and I'd like to get that SRUed back into
  Ubuntu so that we don't accidentally lose this patch in the event of a
  security update or similar.

  [Test Plan]

  William Grant provided this minimal reproducer:

  ```
  root at tmp:~# python3
  Python 3.8.10 (default, May 26 2023, 14:05:08)
  [GCC 9.4.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  >>> import gpg
  >>> c = gpg.Context()
  >>> list(c.keylist())
  []
  >>> fs = []
  >>> for i in range(1024):
  ...     fs.append(open('/dev/null'))
  ...
  >>> list(c.keylist())
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "/usr/lib/python3/dist-packages/gpg/core.py", line 751, in keylist
      key = self.op_keylist_next()
    File "/usr/lib/python3/dist-packages/gpg/core.py", line 1195, in op_keylist_next
      raise excp
    File "/usr/lib/python3/dist-packages/gpg/core.py", line 1190, in op_keylist_next
      errorcheck(gpgme.gpgme_op_keylist_next(self.wrapped, ptr))
    File "/usr/lib/python3/dist-packages/gpg/errors.py", line 129, in errorcheck
      raise GPGMEError(retval, extradata)
  gpg.errors.GPGMEError: GPGME: Too many open files
  ```

  [Where problems could occur]

  `_gpgme_io_select` is pretty central to gpgme, so if something is
  wrong the package will be pretty broken.  On the other hand, that also
  means any glaring problems are likely to be caught by the package's
  test suite.

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