netdev - Re: [PATCH RFC 1/5] vringfd syscall

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Sun, 13 Apr 2008 04:19:54 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Max Krasnyansky <maxk@...lcomm.com>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH RFC 1/5] vringfd syscall

On Sunday 13 April 2008 03:18:20 Marcelo Tosatti wrote:
> I suppose you are doing data copy in ->poll instead of ->read to save
> a system call? This is weird, not conformant to what the interface is
> supposed to do.

Hi Marcelo,

   Thanks for reading this.

   Yeah, I dislike it too.  The main motivation was that not all rings need to 
be "pulled" in this way, but it turns out that userspace can detect this 
(poll, check ring, if nothing, try read, check ring).  So next version will 
unscrew the poll callback.

> > +	/* If they want to use atomically, we have to map the page. */
> > +	if (atomic_use) {
> > +		if (get_user_pages(current, current->mm,
> > +				   (unsigned long)vr->ring.used, 1, 1, 1,
> > +				   &vr->used_page, NULL) != 1) {
>
> Can't the same be achieved by the app mlocking the vring pages, which
> then goes through standard rlimit checking ?

Tun/tap writes to this from any context.  Fortunately, this too is changing, 
as I came up with a sane way of queueing to userspace context for this case.

Expect updated patches Monday.

Thanks!
Rusty.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html