linux-kernel - Re: [PATCH 3/4] fbdev: Add FBINFO_HIDE_SMEM

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Message-Id: <20180910125103eucas1p1e7da7341048a5e54a89e21a94559f576~TCuHaF7jg0750707507eucas1p1q@eucas1p1.samsung.com>
Date:   Mon, 10 Sep 2018 14:51:01 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>, linux-fbdev@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 3/4] fbdev: Add FBINFO_HIDE_SMEM_START flag


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@...sung.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: linux-fbdev@...r.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>

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

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