linux-kernel - Re: [PATCH] drm: Use kvzalloc for allocating blob property memory

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Message-ID: <20180629163832.GF5565@intel.com>
Date:   Fri, 29 Jun 2018 19:38:32 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Michel Dänzer <michel@...nzer.net>
Cc:     David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm: Use kvzalloc for allocating blob property memory

On Fri, Jun 29, 2018 at 06:27:28PM +0200, Michel Dänzer wrote:
> On 2018-06-29 06:12 PM, Ville Syrjälä wrote:
> > On Fri, Jun 29, 2018 at 04:27:10PM +0200, Michel Dänzer wrote:
> >> From: Michel Dänzer <michel.daenzer@....com>
> >>
> >> The property size may be controlled by userspace, can be large (I've
> >> seen failure with order 4, i.e. 16 pages / 64 KB) and doesn't need to be
> >> physically contiguous.
> > 
> > I wonder if we should enforce some kind of reasonable limit
> > on the blob size. Looks like we allow anything up to
> > ULONG_MAX currently. We can't tell at createblob time how
> > the thing is going to be used, so can't have any kind
> > of property specific limit unfortunately.
> 
> The failure I was seeing was for a gamma LUT, so a size limit alone
> cannot solve the issue.

Sure. I was just thinking that maybe we shouldn't allow someone to
allocate unlimited amounts of kernel memory via this interface. But
to do that effectively we'd also need to limit the total amount used
by all blobs.

-- 
Ville Syrjälä
Intel