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

[Erick Archer]

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.arc...@gmx.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