linux-kernel - Re: [PATCH v2] tty: Add comments for tty-ldisc module loading logic

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Date: Fri, 15 Dec 2023 19:49:34 +0530
From: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
To: Zijun Hu <quic_zijuhu@...cinc.com>, <gregkh@...uxfoundation.org>,
        <jirislaby@...nel.org>, <quic_qiancai@...cinc.com>,
        <quic_arandive@...cinc.com>, <quic_saipraka@...cinc.com>,
        <quic_eberman@...cinc.com>
CC: <linux-serial@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tty: Add comments for tty-ldisc module loading logic

Hi,


On 12/15/2023 7:11 PM, Zijun Hu wrote:
> Current tty-ldisc module loading logic within tty_ldisc_get()
> is prone to mislead beginner that the module is able to be loaded
> by a user without capability CAP_SYS_MODULE, add comments to make
> the logic easy to undertand.
>
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
> Changes in v2:
> - Remove condition checking changes
>
>   drivers/tty/tty_ldisc.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
> index 3f68e213df1f..34526ffaccbc 100644
> --- a/drivers/tty/tty_ldisc.c
> +++ b/drivers/tty/tty_ldisc.c
> @@ -150,6 +150,10 @@ static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
>   	 */
>   	ldops = get_ldops(disc);
>   	if (IS_ERR(ldops)) {
> +		/*
> +		 * Always request tty-ldisc module regardless of user's
> +		 * CAP_SYS_MODULE if autoload is enabled.
> +		 */

Without much knowledge of this file...


What the if condition below accomplishes is evident, it probably doesn't 
require a comment.

A more useful comment would be why it does so?

Thank you...

-Vijay/


>   		if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload)
>   			return ERR_PTR(-EPERM);
>   		request_module("tty-ldisc-%d", disc);