From: Chris Wilson <chris@chris-wilson.co.uk>
To: Dan Carpenter <dan.carpenter@oracle.com>,
David Airlie <airlied@linux.ie>
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, Sam Ravnborg <sam@ravnborg.org>,
Emil Velikov <emil.velikov@collabora.com>
Subject: Re: [PATCH] drm/i810: Prevent underflow in ioctl
Date: Fri, 04 Oct 2019 15:08:57 +0100 [thread overview]
Message-ID: <157019813720.18712.6286079822254824652@skylake-alporthouse-com> (raw)
In-Reply-To: <20191004102251.GC823@mwanda>
Quoting Dan Carpenter (2019-10-04 11:22:51)
> The "used" variables here come from the user in the ioctl and it can be
> negative. It could result in an out of bounds write.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> drivers/gpu/drm/i810/i810_dma.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i810/i810_dma.c b/drivers/gpu/drm/i810/i810_dma.c
> index 2a77823b8e9a..e66c38332df4 100644
> --- a/drivers/gpu/drm/i810/i810_dma.c
> +++ b/drivers/gpu/drm/i810/i810_dma.c
> @@ -728,7 +728,7 @@ static void i810_dma_dispatch_vertex(struct drm_device *dev,
> if (nbox > I810_NR_SAREA_CLIPRECTS)
> nbox = I810_NR_SAREA_CLIPRECTS;
>
> - if (used > 4 * 1024)
> + if (used < 0 || used > 4 * 1024)
> used = 0;
Yes, as passed to the GPU instruction, negative used is invalid.
Then it is used as an offset into a memblock, where a negative offset
would be very bad.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris
next prev parent reply other threads:[~2019-10-04 14:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-04 10:22 [PATCH] drm/i810: Prevent underflow in ioctl Dan Carpenter
2019-10-04 14:08 ` Chris Wilson [this message]
2019-10-04 16:04 ` Chris Wilson
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