Re: rpm leaks an fd in install/erase scripts

[Jeff Johnson <n3npq nc rr com>]

Frank Cusack wrote:

> I brought this up wrt openssh a long time ago, on the openssh list.
> I did have a positive response (positive = will fix) from some rpm
> person (not Jeff), but this seems to still be broken as of RH9.
>  

Presumably you mean "has an open fd", rather than "forgets to close"
for "leak". I find it hard to believe that 1 fd per scriptlet execution 
is lost.

If  there's a file descriptor open, it's a rdonly file descriptor positioned
at the end of the payload. I'm not really sure that's a problem.

If you mean that sshd is carrying an open file descriptor, then there's
a missing FD_CLOEXEC that's missing in fdDup() on the payload
file descriptor. I'll take a look ...

IMHO, sshd really needs to be fixed to close file descriptors when
restarted. It's not just rpm %post, and open file descriptors will
remain when sshd is restarted from other contexts. That can be fixed
most easily by closing file descriptors in sshd, not trying to fix each
and every context that might restart sshd.

> 'ssh remotehost sleep 10 & exit' doesn't exit for 10s on Linux.  This
> is because of kernel behavior which doesn't send HUP to background
> processes when the fg process exits, and openssh doesn't exit until
> all read fd's have closed.  That's (arguably) correct behavior.
>
> rpm leaks a dup'd fd to %post et al. scripts.  If a %post (say) [re]starts
> a daemon which only closes fd's 0,1,2, then a command like
> 'ssh remotehost rpm -ivh package.rpm' will hang indefinetely, since stdout
> is still open (daemon running in the bg has the dup'd fd open) and sshd is
> waiting for input.
>
> Are folks aware of this bug?  If I submit a patch, is it likely to be
> applied?  I'd rather not have to dig through the rpm code although I
> will do so if you'll accept a patch and don't have time to look for
> it yourself.

The fix is probably in rpmio/rpmio.c, look for dup call, set FD_CLOEXEC
immediately after, if my guess above is correct.

73 de Jeff