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Date:      Mon, 05 Dec 2016 15:25:24 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-threads@FreeBSD.org
Subject:   [Bug 214540] pam_exec isn't multithreading save
Message-ID:  <bug-214540-16-1L5pUMdp49@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-214540-16@https.bugs.freebsd.org/bugzilla/>
References:  <bug-214540-16@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D214540

--- Comment #2 from Jan Bramkamp <crest@bultmann.eu> ---
I found one case where the same issue in the Linux PAM pam_exec module broke
vsftpd and vsftpd had to workaround the problem because afaik Linux lacks t=
he
required API to avoid this problem completely. I know that pam_exec is a ha=
ck
and should only be used for testing or after very careful analysis on the o=
ther
hand the documentation doesn't warn users about the problem and it's a nasty
layering violation that blow up into the system administrators face and I d=
on't
want to be the poor bastard how has to debug this under time pressure. The =
PAM
policy isn't supposed to inject race conditions into otherwise "working"
applications.

Pointing to a "non-normative recommendation" won't help users bitten by this
problem. My problem with this is that it's a accident waiting to happen and
FreeBSD has the APIs to avoid this whole bug class. To make it worse the on=
es
who will run into the problem (system admins) are often incapable of debugg=
ing
and patching applications complex enough to use pthreads and PAM.

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