[PATCH v4 2/3] perf/x86/intel/uncore: Prefer struct_size over open coded arithmetic

From: Erick Archer
Date: Sat Jun 01 2024 - 12:57:27 EST


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

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

struct intel_uncore_box {
[...]
struct intel_uncore_extra_reg shared_regs[];
};

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_node() function.

This way, the code is more readable and safer.

This code was detected with the help of Coccinelle, and audited and
modified manually.

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]
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
---
arch/x86/events/intel/uncore.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 419c517b8594..b0d518d752aa 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -350,12 +350,11 @@ static void uncore_pmu_init_hrtimer(struct intel_uncore_box *box)
static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type *type,
int node)
{
- int i, size, numshared = type->num_shared_regs ;
+ int i, numshared = type->num_shared_regs;
struct intel_uncore_box *box;

- size = sizeof(*box) + numshared * sizeof(struct intel_uncore_extra_reg);
-
- box = kzalloc_node(size, GFP_KERNEL, node);
+ box = kzalloc_node(struct_size(box, shared_regs, numshared), GFP_KERNEL,
+ node);
if (!box)
return NULL;

--
2.25.1