[PATCH] auth-pam: don't leak PAM env strings after pam_putenv()

[Theo de Raadt]

There are 3 completely seperate PAM libraries:

      Solaris, Linux, and FreeBSD.

You have only checked one of them.

https://docs.oracle.com/cd/E36784_01/html/E36878/pam-putenv-3pam.html

    The pam_putenv() function sets the value of the PAM environment
    variable name equal to value either by altering an existing PAM
    variable or by creating a new one.

One of them documenting this behaviour, and another saying something
different, kind of matters, becaue memory leaks are less dangerous
than use-after-free bugs, which is what your proposal would introduce
if either of the other two PAM libraries follow a different lifetime
rule.