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Subject: Re: [PATCH 3/4] fbdev: Add FBINFO_HIDE_SMEM_START flag
To:     Daniel Vetter <daniel.vetter@ffwll.ch>,
        DRI Development <dri-devel@lists.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>, linux-fbdev@vger.kernel.org,
        Daniel Vetter <daniel.vetter@intel.com>
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Date:   Mon, 10 Sep 2018 14:51:01 +0200
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On 08/22/2018 10:54 AM, Daniel Vetter wrote:
> DRM drivers really, really, really don't want random userspace to
> share buffer behind it's back, bypassing the dma-buf buffer sharing
> machanism. For that reason we've ruthlessly rejected any IOCTL
> exposing the physical address of any graphics buffer.
> 
> Unfortunately fbdev comes with that built-in. We could just set
> smem_start to 0, but that means we'd have to hand-roll our own fb_mmap
> implementation. For good reasons many drivers do that, but
> smem_start/length is still super convenient.
> 
> Hence instead just stop the leak in the ioctl, to keep fb mmap working
> as-is. A second patch will set this flag for all drm drivers.
> 
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: linux-fbdev@vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics