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Subject: Re: [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure
From: Stephen Boyd <sboyd@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, mturquette@baylibre.com
To: Michal Simek <michal.simek@amd.com>, duoming@zju.edu.cn
Date: Thu, 29 Feb 2024 17:22:42 -0800
User-Agent: alot/0.10

Quoting duoming@zju.edu.cn (2024-02-29 06:16:28)
> On Thu, 29 Feb 2024 13:45:54 +0100 Michal Simek wrote:
>=20
> The length of "mio_clk_00x" is 11 bytes, and the kernel will alloc 16 byt=
es to it.
> I use a local variable whose size is 16 bytes to replace it. The detail i=
s shown
> below:
>=20
> 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 =3D 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);
>=20
>         tmp =3D strlen("mio_clk_00x");

Is tmp used now?

> -       clk_name =3D kmalloc(tmp, GFP_KERNEL);
>         for (i =3D 0; i < NUM_MIO_PINS; i++) {
>                 int idx;
>=20
> @@ -439,7 +438,6 @@ static void __init zynq_clk_setup(struct device_node =
*np)
>                 else
>                         can_mio_mux_parents[i] =3D 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);
>=20
> Do you think the above is better?
>=20

It's getting there.