linux-kernel - Re: [PATCH 03/33] mm: slub: add knowledge of reserve pages

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

Message-Id: <200710312146.03351.nickpiggin@yahoo.com.au>
Date:	Wed, 31 Oct 2007 21:46:02 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	netdev@...r.kernel.org, trond.myklebust@....uio.no
Subject: Re: [PATCH 03/33] mm: slub: add knowledge of reserve pages

On Wednesday 31 October 2007 21:42, Peter Zijlstra wrote:
> On Wed, 2007-10-31 at 14:37 +1100, Nick Piggin wrote:
> > On Wednesday 31 October 2007 03:04, Peter Zijlstra wrote:
> > > Restrict objects from reserve slabs (ALLOC_NO_WATERMARKS) to allocation
> > > contexts that are entitled to it.
> > >
> > > Care is taken to only touch the SLUB slow path.
> > >
> > > This is done to ensure reserve pages don't leak out and get consumed.
> >
> > I think this is generally a good idea (to prevent slab allocators
> > from stealing reserve). However I naively think the implementation
> > is a bit overengineered and thus has a few holes.
> >
> > Humour me, what was the problem with failing the slab allocation
> > (actually, not fail but just call into the page allocator to do
> > correct waiting  / reclaim) in the slowpath if the process fails the
> > watermark checks?
>
> Ah, we actually need slabs below the watermarks.

Right, I'd still allow those guys to allocate slabs. Provided they
have the right allocation context, right?


> Its just that once I 
> allocated those slabs using __GFP_MEMALLOC/PF_MEMALLOC I don't want
> allocation contexts that do not have rights to those pages to walk off
> with objects.

And I'd prevent these ones from doing so.

Without keeping track of "reserve" pages, which doesn't feel
too clean.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/