From: Maxime Ripard <mripard@redhat.com>
To: Hans de Goede <hdegoede@redhat.com>
Cc: "Sumit Semwal" <sumit.semwal@linaro.org>,
"Benjamin Gaignard" <benjamin.gaignard@collabora.com>,
"Brian Starkey" <Brian.Starkey@arm.com>,
"John Stultz" <jstultz@google.com>,
"T.J. Mercier" <tjmercier@google.com>,
"Christian König" <christian.koenig@amd.com>,
"Lennart Poettering" <mzxreary@0pointer.de>,
"Robert Mader" <robert.mader@collabora.com>,
"Sebastien Bacher" <sebastien.bacher@canonical.com>,
"Linux Media Mailing List" <linux-media@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
linaro-mm-sig@lists.linaro.org,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Bryan O'Donoghue" <bryan.odonoghue@linaro.org>,
"Milan Zamazal" <mzamazal@redhat.com>,
"Andrey Konovalov" <andrey.konovalov.ynk@gmail.com>
Subject: Re: Safety of opening up /dev/dma_heap/* to physically present users (udev uaccess tag) ?
Date: Mon, 6 May 2024 14:05:12 +0200 [thread overview]
Message-ID: <20240506-dazzling-nippy-rhino-eabccd@houat> (raw)
In-Reply-To: <bb372250-e8b8-4458-bc99-dd8365b06991@redhat.com>
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Hi,
On Mon, May 06, 2024 at 01:49:17PM GMT, Hans de Goede wrote:
> Hi dma-buf maintainers, et.al.,
>
> Various people have been working on making complex/MIPI cameras work OOTB
> with mainline Linux kernels and an opensource userspace stack.
>
> The generic solution adds a software ISP (for Debayering and 3A) to
> libcamera. Libcamera's API guarantees that buffers handed to applications
> using it are dma-bufs so that these can be passed to e.g. a video encoder.
>
> In order to meet this API guarantee the libcamera software ISP allocates
> dma-bufs from userspace through one of the /dev/dma_heap/* heaps. For
> the Fedora COPR repo for the PoC of this:
> https://hansdegoede.dreamwidth.org/28153.html
For the record, we're also considering using them for ARM KMS devices,
so it would be better if the solution wasn't only considering v4l2
devices.
> I have added a simple udev rule to give physically present users access
> to the dma_heap-s:
>
> KERNEL=="system", SUBSYSTEM=="dma_heap", TAG+="uaccess"
>
> (and on Rasperry Pi devices any users in the video group get access)
>
> This was just a quick fix for the PoC. Now that we are ready to move out
> of the PoC phase and start actually integrating this into distributions
> the question becomes if this is an acceptable solution; or if we need some
> other way to deal with this ?
>
> Specifically the question is if this will have any negative security
> implications? I can certainly see this being used to do some sort of
> denial of service attack on the system (1). This is especially true for
> the cma heap which generally speaking is a limited resource.
There's plenty of other ways to exhaust CMA, like allocating too much
KMS or v4l2 buffers. I'm not sure we should consider dma-heaps
differently than those if it's part of our threat model.
> But devices tagged for uaccess are only opened up to users who are
> physcially present behind the machine and those can just hit
> the powerbutton, so I don't believe that any *on purpose* DOS is part of
> the thread model.
How would that work for headless devices?
Maxime
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next prev parent reply other threads:[~2024-05-06 12:05 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-06 11:49 Safety of opening up /dev/dma_heap/* to physically present users (udev uaccess tag) ? Hans de Goede
2024-05-06 12:05 ` Maxime Ripard [this message]
2024-05-06 12:11 ` Hans de Goede
2024-05-06 13:38 ` Daniel Vetter
2024-05-06 14:01 ` Hans de Goede
2024-05-07 11:15 ` Daniel Vetter
2024-05-08 5:46 ` Daniel Stone
2024-05-08 8:33 ` Daniel Vetter
2024-05-08 8:38 ` Daniel Stone
2024-05-08 15:49 ` Daniel Vetter
2024-05-09 9:23 ` Daniel Stone
2024-05-16 10:18 ` Daniel Vetter
2024-05-13 13:51 ` Simon Ser
2024-05-16 10:13 ` Daniel Vetter
2024-05-16 11:49 ` Christian König
2024-05-07 13:34 ` Dmitry Baryshkov
2024-05-07 18:59 ` Laurent Pinchart
2024-05-22 13:34 ` Maxime Ripard
2024-05-23 9:41 ` Daniel Vetter
2024-05-07 13:32 ` Dmitry Baryshkov
2024-05-07 14:34 ` Hans de Goede
2024-05-07 15:09 ` Dmitry Baryshkov
2024-05-07 15:15 ` Bryan O'Donoghue
2024-05-07 15:19 ` Dmitry Baryshkov
2024-05-07 18:40 ` Laurent Pinchart
2024-05-07 19:59 ` Dmitry Baryshkov
2024-05-07 20:15 ` Laurent Pinchart
2024-05-08 8:39 ` Daniel Vetter
2024-05-08 21:54 ` Laurent Pinchart
2024-05-13 8:39 ` Maxime Ripard
2024-05-07 17:36 ` Daniel Vetter
2024-05-07 18:36 ` Laurent Pinchart
2024-05-07 20:07 ` Nicolas Dufresne
2024-05-08 8:36 ` Daniel Vetter
2024-05-08 21:51 ` Laurent Pinchart
2024-05-08 21:52 ` Laurent Pinchart
2024-05-13 8:29 ` Maxime Ripard
2024-05-13 8:34 ` Laurent Pinchart
2024-05-13 15:10 ` Nicolas Dufresne
2024-05-14 20:42 ` Laurent Pinchart
2024-05-15 17:43 ` nicolas.dufresne
2024-05-16 11:27 ` Laurent Pinchart
2024-05-16 17:11 ` nicolas.dufresne
2024-05-21 8:43 ` Maxime Ripard
2024-05-21 14:18 ` nicolas.dufresne
2024-05-16 7:00 ` Simon Ser
2024-05-16 11:20 ` Laurent Pinchart
2024-05-22 13:02 ` Nicolas Dufresne
2024-05-13 13:42 ` Nicolas Dufresne
2024-05-13 13:51 ` Maxime Ripard
2024-05-13 15:06 ` Nicolas Dufresne
2024-05-14 20:45 ` Laurent Pinchart
2024-05-14 20:52 ` Nicolas Dufresne
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