[PATCH] perf/x86/rapl: Prefer struct_size over open coded arithmetic

[Erick Archer <erick.archer@gmx.com>]

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].

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

struct rapl_pmus {
	[...]
	struct rapl_pmu *pmus[] __counted_by(maxdie);
};

the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the calculation "size + count * size" in
the 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@gmx.com>
---
 arch/x86/events/rapl.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index fb2b1961e5a3..8ef08b5d55a7 100644
--- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -675,10 +675,8 @@ static const struct attribute_group *rapl_attr_update[] = {
 static int __init init_rapl_pmus(void)
 {
 	int maxdie = topology_max_packages() * topology_max_dies_per_package();
-	size_t size;

-	size = sizeof(*rapl_pmus) + maxdie * sizeof(struct rapl_pmu *);
-	rapl_pmus = kzalloc(size, GFP_KERNEL);
+	rapl_pmus = kzalloc(struct_size(rapl_pmus, pmus, maxdie), GFP_KERNEL);
 	if (!rapl_pmus)
 		return -ENOMEM;

--
2.25.1