linux-kernel - Re: [PATCH 3/3] i2c: i801: avoid panic if ioreamp fails

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Date:   Fri, 10 May 2019 10:09:55 +0200
From:   Jean Delvare <jdelvare@...e.de>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     <linux-kernel@...r.kernel.org>, Wolfram Sang <wsa@...-dreams.de>,
        <linux-i2c@...r.kernel.org>, Hulk Robot <hulkci@...wei.com>
Subject: Re: [PATCH 3/3] i2c: i801: avoid panic if ioreamp fails

Hi Kefeng,

On Fri, 10 May 2019 11:03:20 +0800, Kefeng Wang wrote:
> If ioremap fails, NULL pointer dereference will happen and
> leading to a kernel panic when access the virtual address
> in check_signature().
> 
> Fix it by check the return value of ioremap.
> 
> Cc: Jean Delvare <jdelvare@...e.com>
> Cc: Wolfram Sang <wsa@...-dreams.de>
> Cc: linux-i2c@...r.kernel.org
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  drivers/i2c/busses/i2c-i801.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index 679c6c41f64b..fc6ccb8aba17 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -1068,7 +1068,10 @@ static void __init input_apanel_init(void)
>  	void __iomem *bios;
>  	const void __iomem *p;
>  
> -	bios = ioremap(0xF0000, 0x10000); /* Can't fail */
> +	bios = ioremap(0xF0000, 0x10000);
> +	if (!base)

That would be "if (!bios)". Please don't send patches without at least
test-building the result.

We don't need this anyway. The comment says it can't fail, so why
bother checking for a condition which will never happen?

> +		return -ENOMEM;
> +
>  	p = bios_signature(bios);
>  	if (p) {
>  		/* just use the first address */


-- 
Jean Delvare
SUSE L3 Support