netdev - [PATCH] net: wwan: t7xx: Prefer struct_size over open coded arithmetic

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Date: Sat, 24 Feb 2024 19:19:32 +0100
From: Erick Archer <erick.archer@....com>
To: Chandrashekar Devegowda <chandrashekar.devegowda@...el.com>,
	Chiranjeevi Rapolu <chiranjeevi.rapolu@...ux.intel.com>,
	Liu Haijun <haijun.liu@...iatek.com>,
	M Chetan Kumar <m.chetan.kumar@...ux.intel.com>,
	Ricardo Martinez <ricardo.martinez@...ux.intel.com>,
	Loic Poulain <loic.poulain@...aro.org>,
	Sergey Ryazanov <ryazanov.s.a@...il.com>,
	Johannes Berg <johannes@...solutions.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Kees Cook <keescook@...omium.org>
Cc: Erick Archer <erick.archer@....com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] net: wwan: t7xx: 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][2].

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

struct port_proxy {
	[...]
	struct t7xx_port ports[];
};

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
devm_kzalloc() function.

This way, the code is more readable and 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/net/wwan/t7xx/t7xx_port_proxy.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wwan/t7xx/t7xx_port_proxy.c b/drivers/net/wwan/t7xx/t7xx_port_proxy.c
index 8f5e01705af2..7d6388bf1d7c 100644
--- a/drivers/net/wwan/t7xx/t7xx_port_proxy.c
+++ b/drivers/net/wwan/t7xx/t7xx_port_proxy.c
@@ -543,8 +543,10 @@ static int t7xx_proxy_alloc(struct t7xx_modem *md)
 	struct device *dev = &md->t7xx_dev->pdev->dev;
 	struct port_proxy *port_prox;

-	port_prox = devm_kzalloc(dev, sizeof(*port_prox) +
-				 sizeof(struct t7xx_port) * T7XX_MAX_POSSIBLE_PORTS_NUM,
+	port_prox = devm_kzalloc(dev,
+				 struct_size(port_prox,
+					     ports,
+					     T7XX_MAX_POSSIBLE_PORTS_NUM),
 				 GFP_KERNEL);
 	if (!port_prox)
 		return -ENOMEM;
--
2.25.1