linux-kernel - [PATCH 3.12 083/123] drm: add a check for x/y in drm_mode

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Date:	Tue,  4 Aug 2015 16:40:27 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Zhao Junwang <zhjwpku@...il.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 083/123] drm: add a check for x/y in drm_mode_setcrtc

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

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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: Jiri Slaby <jslaby@...e.cz>
---
 drivers/gpu/drm/drm_crtc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index bff2fa941f60..b382df64c4f2 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2071,8 +2071,11 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
 	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;
 
 	drm_modeset_lock_all(dev);
-- 
2.5.0

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