linux-kernel - Re: [PATCH] printk: handle blank console arguments passed in.

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Message-ID: <20200515152418.GH7340@linux-b0ei>
Date:   Fri, 15 May 2020 17:24:18 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Shreyas Joshi <shreyas.joshi@...mp.com>
Cc:     sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: handle blank console arguments passed in.

On Mon 2020-03-09 15:29:15, Shreyas Joshi wrote:
> If uboot passes a blank string to console_setup then it results in a trashed memory.
> Ultimately, the kernel crashes during freeing up the memory. This fix checks if there
> is a blank parameter being passed to console_setup from uboot.
> In case it detects that the console parameter is blank then
> it doesn't setup the serial device and it gracefully exits.
> 
> Signed-off-by: Shreyas Joshi <shreyas.joshi@...mp.com>
> ---
>  kernel/printk/printk.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index ad4606234545..e9ad730991e0 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2165,7 +2165,10 @@ static int __init console_setup(char *str)
>  	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
>  	char *s, *options, *brl_options = NULL;
>  	int idx;
> -
> +	if (str[0] == 0) {
> +		console_loglevel = 0;

What is the reason to set console_loglevel here, please?

> +		return 1;
> +	}

Anyway, for example, earlycon parameter is allowed to be used with
empty string when the console parameters can be set via ACPI SPCR,
see param_setup_earlycon(). Therefore I am afraid that every setup()
function has to handle this on its own and this patch makes sense.

Best Regards,
Petr