linux-kernel - [PATCH 3.2 074/110] drm: add a check for x/y in drm_mode

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Message-ID: <lsq.1439201551.667522004@decadent.org.uk>
Date:	Mon, 10 Aug 2015 12:12:31 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Zhao Junwang" <zhjwpku@...il.com>,
	"Daniel Vetter" <daniel.vetter@...ll.ch>
Subject: [PATCH 3.2 074/110] drm: add a check for x/y in drm_mode_setcrtc

3.2.71-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Zhao Junwang <zhjwpku@...il.com>

commit 01447e9f04ba1c49a9534ae6a5a6f26c2bb05226 upstream.

legacy setcrtc ioctl does take a 32 bit value which might indeed
overflow

the checks of crtc_req->x > INT_MAX and crtc_req->y > INT_MAX aren't
needed any more with this

v2: -polish the annotation according to Daniel's comment

Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Zhao Junwang <zhjwpku@...il.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/drm_crtc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1505,8 +1505,11 @@ int drm_mode_setcrtc(struct drm_device *
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return -EINVAL;
 
-	/* For some reason crtc x/y offsets are signed internally. */
-	if (crtc_req->x > INT_MAX || crtc_req->y > INT_MAX)
+	/*
+	 * Universal plane src offsets are only 16.16, prevent havoc for
+	 * drivers using universal plane code internally.
+	 */
+	if (crtc_req->x & 0xffff0000 || crtc_req->y & 0xffff0000)
 		return -ERANGE;
 
 	mutex_lock(&dev->mode_config.mutex);

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