linux-kernel - Re: [PATCH 2/3] drm/scheduler: Fix UAF in drm_sched_fence_get_timeline

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Message-ID: <18a77f80e2dfed630d22b9d6246c7d2122629a5a.camel@pengutronix.de>
Date:   Thu, 02 Nov 2023 12:19:40 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Airlie <airlied@...il.com>
Cc:     asahi@...ts.linux.dev, Asahi Lina <lina@...hilina.net>,
        Luben Tuikov <ltuikov89@...il.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        alyssa@...enzweig.io, Sumit Semwal <sumit.semwal@...aro.org>,
        Faith Ekstrand <faith.ekstrand@...labora.com>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 2/3] drm/scheduler: Fix UAF in
 drm_sched_fence_get_timeline_name

Am Donnerstag, dem 02.11.2023 um 11:48 +0100 schrieb Christian König:
[...]
> I was considering to change the dma_fence semantics so that 
> dma_fence_signal() could only be called from the interrupt contexts of 
> devices and then put a big fat WARN_ON(!in_interrupt()) in there.
> 
> It's a sledgehammer, but as far as I can see the only thing which might 
> help. Opinions?

That's not going to fly. As soon as you are dealing with device drivers
that use IRQ threads, either voluntarily or even involuntarily on RT
kernels, the dma_fence_signal will be from process context.

Regards,
Lucas