netdev - Re: [PATCH] nf_conntrack: avoid kernel pointer value leak in slab name

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Message-ID: <20160514213322.GD9763@1wt.eu>
Date:	Sat, 14 May 2016 23:33:22 +0200
From:	Willy Tarreau <w@....eu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Network Development List <netdev@...r.kernel.org>
Subject: Re: [PATCH] nf_conntrack: avoid kernel pointer value leak in slab
 name

On Sat, May 14, 2016 at 02:31:04PM -0700, Linus Torvalds wrote:
> On Sat, May 14, 2016 at 11:24 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> >
> > -       net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%p", net);
> > +       net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%llu",
> > +                               (u64)atomic64_inc_return(&unique_id));
> 
> Oh well. I suspect this is going to cause a new warning on alpha and
> ia64 and possibly others.
> 
> "u64" is indeed "unsigned long long" on x86 and many other
> architectures, but on alpga and ia64 it's just "unsigned long".
> 
> So that case should have been to "long long". I detest how there isn't
> a "64-bit size" printf specifier.

Why simply not cast the atomic to (unsigned long long) instead of (u64)
so that %llu always matches ?

Willy