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Subject: [Bug 214540] pam_exec isn't multithreading save
Date: Tue, 15 Nov 2016 17:01:37 +0000
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X-Bugzilla-Product: Base System
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X-Bugzilla-Version: 11.0-RELEASE
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X-Bugzilla-Severity: Affects Some People
X-Bugzilla-Who: crest@bultmann.eu
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D214540

            Bug ID: 214540
           Summary: pam_exec isn't multithreading save
           Product: Base System
           Version: 11.0-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: threads
          Assignee: freebsd-threads@FreeBSD.org
          Reporter: crest@bultmann.eu

The pam_exec module uses vfork()+execve() and waitpid() to spawn a child
process and wait for its completion. This is a race condition in a
multithreaded process using PAM. An other thread could reap the process for=
ked
by pam_exec in which case waitpid() would either fail because there is no v=
alid
pid to wait for or wait for the wrong process if it happens to reuse the pi=
d.
The correct solution would be to use pdfork() and wait with kevent() on the
(EVFILT_PROCDESC, process descriptor) event.

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