vsftpd hangs with SIGCHLD when pam_exec.so is used

[Markus Wigge]

When you try to run a script with pam_exec.so on login vsftpd freezes with SIGCHLD.

This was fixed in 2015 by redhat and never adopted to Debian/Ubunutu.

See also:
- https://bugzilla.redhat.com/show_bug.cgi?id=1198259
- https://git.centos.org/rpms/vsftpd/blob/54ac5fac29fcc1bb68f2e96e63ecfda655286ff8/f/SOURCES/0026-Prevent-hanging-in-SIGCHLD-handler.patch

[Mitchell Dzurick (mitchdz)]

Thank you for taking the time to make this bug report Markus!

[Mitchell Dzurick (mitchdz)]

What version of Ubuntu are you seeing this bug on? Unfortunately upstream/debian has been pretty dormant for a while, in-fact we are ahead of debian right now, so it may make sense to apply this patch.

Unfortunately it looks like even upstream does not have this patch applied.

[Mitchell Dzurick (mitchdz)]

Markus, if I were to create a PPA with this patch applied, would you be willing to help test that out?

[Markus Wigge (markus-cultcom)]

Hello,

actually I am running "bookworm" and noticed that the packet is quite
abandoned so I looked at the Ubuntu repository which had a newer release
of vsftpd but also quite old.

I build the ubuntu package on debian bookworm an noticed the same error.
Then I rebuilt the same package with the attached patch applied and now
it is working as expected. My custom script is run by pam_exec.so on
login as it was intended.

It would be great to see it applied upstream in Ubunutu and Debian as well.

Just add a line to /etc/pam.d/vsftpd like this:
account optional pam_exec.so debug quiet /root/my_script.sh

And simply run "logger test" inside.

Without the patch the vsftpd hangs as soon as someone logs in.

Kind Regards,
Markus

Am 15.06.24 um 02:50 schrieb Mitchell Dzurick:
> Markus, if I were to create a PPA with this patch applied, would you be
> willing to help test that out?
>
> ** Changed in: vsftpd (Ubuntu)
> Status: New => Triaged
>

[Mitchell Dzurick (mitchdz)]

Markus, would you mind making a bug report upstream to see if this could be included?

[Markus Wigge (markus-cultcom)]

Well, there is a bug report from 2020 about the problem:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=952421

Am 18.06.24 um 21:01 schrieb Mitchell Dzurick:
> Markus, would you mind making a bug report upstream to see if this could
> be included?
>

[Paride Legovini (paride)]

Looks like upstream development is *very* slow, and I could not find an issue tracker or a public vcs repo. Given that we have Ubuntu delta already (we're already ahead of Debian, which is still packaging 3.0.3), I believe it makes sense to add the patch to the Ubuntu package.

[Mitchell Dzurick (mitchdz)]

Markus, if we prepare a package with the patch, would you be willing to help out testing the patch?