memstick: jmb38x_ms: Prefer struct_size over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@gmx.com>
Link: https://lore.kernel.org/r/20210911131933.2089-1-len.baker@gmx.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/memstick/host/jmb38x_ms.c b/drivers/memstick/host/jmb38x_ms.c
index f9a93b0..a7a0f0c 100644 (file)
--- a/drivers/memstick/host/jmb38x_ms.c
+++ b/drivers/memstick/host/jmb38x_ms.c
@@ -927,8 +927,7 @@ static int jmb38x_ms_probe(struct pci_dev *pdev,
                goto err_out_int;
        }
 
-       jm = kzalloc(sizeof(struct jmb38x_ms)
-                    + cnt * sizeof(struct memstick_host *), GFP_KERNEL);
+       jm = kzalloc(struct_size(jm, hosts, cnt), GFP_KERNEL);
        if (!jm) {
                rc = -ENOMEM;
                goto err_out_int;