Date: Fri, 6 Nov 2009 09:57:20 +0100 From: Attilio Rao <attilio@freebsd.org> To: "Dorr H. Clark" <dclark@engr.scu.edu> Cc: freebsd-hackers@freebsd.org, freebsd-bugs@freebsd.org, freebsd-stable@freebsd.org Subject: Re: resource leak in fifo_vnops.c: 6.x/7.x/8.x Message-ID: <3bbf2fe10911060057t5ebfb330n486c80018826fa93@mail.gmail.com> In-Reply-To: <Pine.GSO.4.21.0911051701520.13698-100000@nova48.dc.engr.scu.edu> References: <Pine.GSO.4.21.0911041504420.29358-100000@nova32.dc.engr.scu.edu> <Pine.GSO.4.21.0911051701520.13698-100000@nova48.dc.engr.scu.edu>
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2009/11/6 Dorr H. Clark <dclark@engr.scu.edu>:
>
>
> We believe we have identified a significant resource leak
> present in 6.x, 7.x, and 8.x. We believe this is a regression
> versus FreeBSD 4.x which appears to do the Right Thing (tm).
>
> We have a test program (see below) which will run the system
> out of sockets by repeated exercise of the failing code
> path in the kernel.
>
> Our proposed fix is applied to the file usr/src/sys/fs/fifofs/fifo_vnops.c
>
>
> @@ -237,6 +237,8 @@
> if (ap->a_mode & FWRITE) {
> if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
> mtx_unlock(&fifo_mtx);
> + /* Exclusive VOP lock is held - safe to clean */
> + fifo_cleanup(vp);
> return (ENXIO);
> }
> fip->fi_writers++;
I think it should also check that fip->if_writers == 0 (and possibly
the checks within fifo_cleanup() should just be assertions, but that's
orthogonal someway) and the comment is not needed.
Attilio
--
Peace can only be achieved by understanding - A. Einstein
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