Linux-PAM and saslauthd process reaping conflict

[Jov]

Hello,

my apologies for crossposting. I am unsure which project this should be
fixed in, if not both.

When you use saslauthd with pam_exec.so, a process reaping race is
created. pam_exec.c uses a fork/waitpid combination to run it's child
process and saslauthd has a signal handler for SIGCHLD. If the process
terminates before the waitpid is entered, the SIGCHLD is handled by
saslauthd and pam_exec returns with an error to the pam stack.

I tried fixing it in PAM by restoring the default sighandler but this
did not seem to work (see patch). Perhaps I made a silly mistake or it
has something to do with MT signal handling, I do not know. In any case,
it seems a bad idea for PAM to assume there is no SIGCHLD handler
installed in the parent process.

Eventually, I fixed it by disabling automatic process reaping in
saslautd with the pam authentication mechanism. Afaict, this handler is
not used anyway.

Regards,

Johan Verrept


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