Re: [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure

From: Stephen Boyd <sboyd@kernel.org>
To: Michal Simek <michal.simek@amd.com>, duoming@zju.edu.cn
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
	mturquette@baylibre.com
Subject: Re: [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure
Date: Thu, 29 Feb 2024 17:22:42 -0800	[thread overview]
Message-ID: <856febae4f00b1129f695cf3c75dd380.sboyd@kernel.org> (raw)
In-Reply-To: <365f9a90.55b0.18df5394935.Coremail.duoming@zju.edu.cn>

Quoting duoming@zju.edu.cn (2024-02-29 06:16:28)
> On Thu, 29 Feb 2024 13:45:54 +0100 Michal Simek wrote:
> 
> The length of "mio_clk_00x" is 11 bytes, and the kernel will alloc 16 bytes to it.
> I use a local variable whose size is 16 bytes to replace it. The detail is shown
> below:
> 
> diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
> index 7bdeaff2bfd..81d530e3357 100644
> --- a/drivers/clk/zynq/clkc.c
> +++ b/drivers/clk/zynq/clkc.c
> @@ -215,7 +215,7 @@ static void __init zynq_clk_setup(struct device_node *np)
>         int i;
>         u32 tmp;
>         int ret;
> -       char *clk_name;
> +       char clk_name[16];
>         unsigned int fclk_enable = 0;
>         const char *clk_output_name[clk_max];
>         const char *cpu_parents[4];
> @@ -427,7 +427,6 @@ static void __init zynq_clk_setup(struct device_node *np)
>                         SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock);
> 
>         tmp = strlen("mio_clk_00x");

Is tmp used now?

> -       clk_name = kmalloc(tmp, GFP_KERNEL);
>         for (i = 0; i < NUM_MIO_PINS; i++) {
>                 int idx;
> 
> @@ -439,7 +438,6 @@ static void __init zynq_clk_setup(struct device_node *np)
>                 else
>                         can_mio_mux_parents[i] = dummy_nm;
>         }
> -       kfree(clk_name);
>         clk_register_mux(NULL, "can_mux", periph_parents, 4,
>                         CLK_SET_RATE_NO_REPARENT, SLCR_CAN_CLK_CTRL, 4, 2, 0,
>                         &canclk_lock);
> 
> Do you think the above is better?
> 

It's getting there.