[PATCH] irqchip/qcom: Use struct_size() in devm_kzalloc()

From: Gustavo A. R. Silva
Date: Tue Jun 04 2019 - 19:43:02 EST

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
int stuff;
struct boo entry[];

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = devm_kzalloc(dev, size, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = devm_kzalloc(dev, struct_size(instance, entry, count), GFP_KERNEL);

Notice that, in this case, variable alloc_sz is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
drivers/irqchip/qcom-irq-combiner.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/qcom-irq-combiner.c b/drivers/irqchip/qcom-irq-combiner.c
index 7f0c0be322e0..d269a7722032 100644
--- a/drivers/irqchip/qcom-irq-combiner.c
+++ b/drivers/irqchip/qcom-irq-combiner.c
@@ -237,7 +237,6 @@ static int get_registers(struct platform_device *pdev, struct combiner *comb)
static int __init combiner_probe(struct platform_device *pdev)
struct combiner *combiner;
- size_t alloc_sz;
int nregs;
int err;

@@ -247,8 +246,8 @@ static int __init combiner_probe(struct platform_device *pdev)
return -EINVAL;

- alloc_sz = sizeof(*combiner) + sizeof(struct combiner_reg) * nregs;
- combiner = devm_kzalloc(&pdev->dev, alloc_sz, GFP_KERNEL);
+ combiner = devm_kzalloc(&pdev->dev, struct_size(combiner, regs, nregs),
if (!combiner)
return -ENOMEM;