linux-kernel - Re: [PATCH] riscv: Use kcalloc() instead of kzalloc()

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Date: Mon, 22 Jan 2024 09:52:33 +0100
From: Andrew Jones <ajones@...tanamicro.com>
To: Erick Archer <erick.archer@....com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Conor Dooley <conor.dooley@...rochip.com>, Evan Green <evan@...osinc.com>, 
	Clément Léger <cleger@...osinc.com>, Jisheng Zhang <jszhang@...nel.org>, 
	Charlie Jenkins <charlie@...osinc.com>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] riscv: Use kcalloc() instead of kzalloc()

On Sat, Jan 20, 2024 at 02:54:00PM +0100, Erick Archer wrote:
> 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 purpose specific kcalloc() function instead of the argument
> count * size in the kzalloc() function.
> 
> Also, it is preferred to use sizeof(*pointer) instead of sizeof(type)
> due to the type of the variable can change and one needs not change the
> former (unlike the latter).
> 
> Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Link: https://github.com/KSPP/linux/issues/162
> Signed-off-by: Erick Archer <erick.archer@....com>
> ---
>  arch/riscv/kernel/cpufeature.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 89920f84d0a3..549a76e34c4e 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -901,8 +901,7 @@ static int check_unaligned_access_all_cpus(void)
>  {
>  	unsigned int cpu;
>  	unsigned int cpu_count = num_possible_cpus();
> -	struct page **bufs = kzalloc(cpu_count * sizeof(struct page *),
> -				     GFP_KERNEL);
> +	struct page **bufs = kcalloc(cpu_count, sizeof(*bufs), GFP_KERNEL);
> 
>  	if (!bufs) {
>  		pr_warn("Allocation failure, not measuring misaligned performance\n");
> --
> 2.25.1
>

Reviewed-by: Andrew Jones <ajones@...tanamicro.com>