[lug] Wierd C issue. qmail and vpopmail

D. Stimits stimits at idcomm.com
Sat Apr 21 14:05:57 MDT 2001

John Starkey wrote:
> I'm using vpopmail and at random times it will lose domains and users.
> Although everything is still there. All mail is being queued but not
> delivered to the box. Obviously qmail knows the users exist and there
> are entries in control/virtualhosts. But at the same time users are
> unable to log in to retrieve their email (via POP or IMAP), the error
> being a general "user not found". They are being, or trying to be,
> authenticated via vpopmail's auth app (vchkpw) after qmail-popup and
> before qmail-pop3d.
> If I move the domain's folder out of the way and add the domains and
> users again and then move the folder back everything is fine til next
> time.
> I did an strace on the function that adds new users and I'm finding that
> for the domains that are disappearing (and before I replace them) that
> the open() function is being warped with wierd random characters instead
> of the path. The actual file name is correct but the path leading to it
> is trashed. An strace on a deleted and replaced domain is fine and
> legible.
> Can anyone even guess as to what might be causing this?  I've recompiled
> and installed and it still does this. I've spent a lot of hours working
> on setting this up, I'd rather replace a line of code if I can find it
> than to research and config another app, at this point.

It sounds like a legitimate bug that the authors might be interested in
fixing (it sounds like a problem working with null-terminated strings).
One very minor possibility is that someone is trying to run a buffer
overflow on it. If you know the exact time that it first fails, and a
prior time when it worked, you might check logs to see what happened in
the time between. So, there is my "guess" set; the main difference
between the first and second possibility is whether the bug is being
found in normal operation or intentionally, either way it is still
probably a bug needing a patch.

D. Stimits, stimits at idcomm.com

> Thanks,
> John
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