[PATCH 0/2] rcu: Use kcalloc() instead of kzalloc()

[PATCH 0/2] rcu: Use kcalloc() instead of kzalloc()

[Qianfeng Rong]

Replace kzalloc() with kcalloc() in kernel/rcu.  As noted in the kernel
documentation [1], open-coded multiplication in allocator arguments is
discouraged because it can lead to integer overflow.

Use kcalloc() to gain built-in overflow protection, making memory
allocation safer when calculating allocation size compared to explicit
multiplication.

Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments #1
Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>

Qianfeng Rong (2):
  rcutorture: Use kcalloc() instead of kzalloc()
  refscale: Use kcalloc() instead of kzalloc()

 kernel/rcu/rcutorture.c | 4 ++--
 kernel/rcu/refscale.c   | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

-- 
2.34.1

[PATCH 1/2] rcutorture: Use kcalloc() instead of kzalloc()

[Qianfeng Rong]

Use kcalloc() in rcu_torture_writer() to gain built-in overflow protection,
making memory allocation safer when calculating allocation size compared to
explicit multiplication.

Change sizeof(ulo[0]) and sizeof(rgo[0]) to sizeof(*ulo) and sizeof(*rgo),
as this is more consistent with coding conventions.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
---
 kernel/rcu/rcutorture.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7a893d51d02b..60cac761efc9 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1571,12 +1571,12 @@ rcu_torture_writer(void *arg)
 		return 0;
 	}
 	if (cur_ops->poll_active > 0) {
-		ulo = kzalloc(cur_ops->poll_active * sizeof(ulo[0]), GFP_KERNEL);
+		ulo = kcalloc(cur_ops->poll_active, sizeof(*ulo), GFP_KERNEL);
 		if (!WARN_ON(!ulo))
 			ulo_size = cur_ops->poll_active;
 	}
 	if (cur_ops->poll_active_full > 0) {
-		rgo = kzalloc(cur_ops->poll_active_full * sizeof(rgo[0]), GFP_KERNEL);
+		rgo = kcalloc(cur_ops->poll_active_full, sizeof(*rgo), GFP_KERNEL);
 		if (!WARN_ON(!rgo))
 			rgo_size = cur_ops->poll_active_full;
 	}
-- 
2.34.1

[PATCH 2/2] refscale: Use kcalloc() instead of kzalloc()

[Qianfeng Rong]

Use kcalloc() in main_func() to gain built-in overflow protection, making
memory allocation safer when calculating allocation size compared to
explicit multiplication.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
---
 kernel/rcu/refscale.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index df646e0694a8..5840fac06feb 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -1021,7 +1021,7 @@ static int main_func(void *arg)
 	set_user_nice(current, MAX_NICE);
 
 	VERBOSE_SCALEOUT("main_func task started");
-	result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
+	result_avg = kcalloc(nruns, sizeof(*result_avg), GFP_KERNEL);
 	buf = kzalloc(800 + 64, GFP_KERNEL);
 	if (!result_avg || !buf) {
 		SCALEOUT_ERRSTRING("out of memory");
-- 
2.34.1

Re: [PATCH 0/2] rcu: Use kcalloc() instead of kzalloc()

[Paul E. McKenney]

On Thu, Aug 21, 2025 at 09:41:15PM +0800, Qianfeng Rong wrote:
> Replace kzalloc() with kcalloc() in kernel/rcu.  As noted in the kernel
> documentation [1], open-coded multiplication in allocator arguments is
> discouraged because it can lead to integer overflow.
> 
> Use kcalloc() to gain built-in overflow protection, making memory
> allocation safer when calculating allocation size compared to explicit
> multiplication.
> 
> Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments #1
> Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>

Queued for review and testing, thank you!

							Thanx, Paul

> Qianfeng Rong (2):
>   rcutorture: Use kcalloc() instead of kzalloc()
>   refscale: Use kcalloc() instead of kzalloc()
> 
>  kernel/rcu/rcutorture.c | 4 ++--
>  kernel/rcu/refscale.c   | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> -- 
> 2.34.1
>