linux-hardening - [PATCH][next] drm/gud: Use size_add() in call to struct

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Date:   Fri, 15 Sep 2023 12:43:20 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Noralf Trønnes <noralf@...nnes.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Peter Stuge <peter@...ge.se>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] drm/gud: Use size_add() in call to struct_size()

If, for any reason, the open-coded arithmetic causes a wraparound, the
protection that `struct_size()` adds against potential integer overflows
is defeated. Fix this by hardening call to `struct_size()` with `size_add()`.

Fixes: 40e1a70b4aed ("drm: Add GUD USB Display driver")
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/gpu/drm/gud/gud_pipe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
index d2f199ea3c11..a02f75be81f0 100644
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -503,7 +503,7 @@ int gud_pipe_check(struct drm_simple_display_pipe *pipe,
 		return -ENOENT;
 
 	len = struct_size(req, properties,
-			  GUD_PROPERTIES_MAX_NUM + GUD_CONNECTOR_PROPERTIES_MAX_NUM);
+			  size_add(GUD_PROPERTIES_MAX_NUM, GUD_CONNECTOR_PROPERTIES_MAX_NUM));
 	req = kzalloc(len, GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;
-- 
2.34.1