From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: Add to_user_ptr()
Date: Mon, 25 Feb 2013 12:58:01 +0200 [thread overview]
Message-ID: <20130225105801.GQ4469@intel.com> (raw)
In-Reply-To: <m2zjyww1c5.fsf@firstfloor.org>
On Fri, Feb 22, 2013 at 12:16:58PM -0800, Andi Kleen wrote:
> ville.syrjala@linux.intel.com writes:
>
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > to_user_ptr() simply casts a pointer passed as u64 from user space
> > to void __user * correctly. Using this lets us get rid of all the
> > tiresome casts.
>
> The whole point of __user is to track it elsewhere to avoid mistakes,
> which may result in security bugs.
>
> A __user cast usually means your tracking is not complete, it's
> supposed to be ugly so that you fix the tracking. Prettying
> it defeats that point.
>
> How about just changing the original field to a pointer and add
> the __user there?
That would introduce 32bit vs. 64bit issues. We pass all user space
pointer as __u64 precisely to avoid such issues.
--
Ville Syrjälä
Intel OTC
prev parent reply other threads:[~2013-02-25 10:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-22 14:12 [PATCH] drm/i915: Add to_user_ptr() ville.syrjala
2013-02-22 14:29 ` Chris Wilson
2013-03-03 18:50 ` Daniel Vetter
[not found] ` <m2zjyww1c5.fsf@firstfloor.org>
2013-02-25 10:58 ` Ville Syrjälä [this message]
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