[3.5.y.z extended stable] Patch "drm: Prevent overwriting from userspace underallocating core ioctl" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Wed Nov 6 10:40:14 UTC 2013

This is a note to let you know that I have just added a patch titled

    drm: Prevent overwriting from userspace underallocating core ioctl

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From c0614f3697a7cbaa3ef53b8ef64866797e5112c0 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Wed, 16 Oct 2013 11:22:44 +0100
Subject: drm: Prevent overwriting from userspace underallocating core ioctl
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit b062672e305ce071f21eb9e18b102c2a430e0999 upstream.

Apply the protections from

commit 1b2f1489633888d4a06028315dc19d65768a1c05
Author: Dave Airlie <airlied at redhat.com>
Date:   Sat Aug 14 20:20:34 2010 +1000

    drm: block userspace under allocating buffer and having drivers overwrite it (v2)

to the core ioctl structs as well, for we found one instance where there
is a 32-/64-bit size mismatch and were guilty of writing beyond the end
of the user's buffer.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Dave Airlie <airlied at redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied at redhat.com>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/gpu/drm/drm_drv.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 8a9d079..df54da9 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -422,9 +422,16 @@ long drm_ioctl(struct file *filp,
 			asize = drv_size;
 	else if ((nr >= DRM_COMMAND_END) || (nr < DRM_COMMAND_BASE)) {
+		u32 drv_size;
 		ioctl = &drm_ioctls[nr];
-		cmd = ioctl->cmd;
+		drv_size = _IOC_SIZE(ioctl->cmd);
 		usize = asize = _IOC_SIZE(cmd);
+		if (drv_size > asize)
+			asize = drv_size;
+		cmd = ioctl->cmd;
 	} else
 		goto err_i1;


More information about the kernel-team mailing list