linux-hardening - [PATCH] drm/xe: Prefer struct_size over open coded arithmetic

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Date: Sat, 10 Feb 2024 15:19:12 +0100
From: Erick Archer <erick.archer@....com>
To: Lucas De Marchi <lucas.demarchi@...el.com>,
	Oded Gabbay <ogabbay@...nel.org>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Kees Cook <keescook@...omium.org>
Cc: Erick Archer <erick.archer@....com>,
	intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] drm/xe: Prefer struct_size over open coded arithmetic

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1].

As the "q" variable is a pointer to "struct xe_exec_queue" and this
structure ends in a flexible array:

struct xe_exec_queue {
	[...]
	struct xe_lrc lrc[];
};

the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the argument "size + size * count" in the
kzalloc() function.

This way, the code is more readable and more safer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <erick.archer@....com>
---
 drivers/gpu/drm/xe/xe_exec_queue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
index bcfc4127c7c5..f4e53cbccd04 100644
--- a/drivers/gpu/drm/xe/xe_exec_queue.c
+++ b/drivers/gpu/drm/xe/xe_exec_queue.c
@@ -44,7 +44,7 @@ static struct xe_exec_queue *__xe_exec_queue_create(struct xe_device *xe,
 	/* only kernel queues can be permanent */
 	XE_WARN_ON((flags & EXEC_QUEUE_FLAG_PERMANENT) && !(flags & EXEC_QUEUE_FLAG_KERNEL));

-	q = kzalloc(sizeof(*q) + sizeof(struct xe_lrc) * width, GFP_KERNEL);
+	q = kzalloc(struct_size(q, lrc, width), GFP_KERNEL);
 	if (!q)
 		return ERR_PTR(-ENOMEM);

--
2.25.1