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Date:   Tue, 8 Aug 2023 22:17:12 +0200
From:   Samuel Thibault <samuel.thibault@ens-lyon.org>
To:     =?utf-8?Q?G=C3=BCnther?= Noack <gnoack3000@gmail.com>
Cc:     Kees Cook <keescook@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Simon Brand <simon.brand@postadigitale.de>,
        linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
Subject: Re: [PATCH] TIOCSTI: Document CAP_SYS_ADMIN behaviour in Kconfig
Message-ID: <20230808201712.efl6vbtsuy57b64d@begin>
Mail-Followup-To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
        =?utf-8?Q?G=C3=BCnther?= Noack <gnoack3000@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Simon Brand <simon.brand@postadigitale.de>,
        linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
References: <20230808201115.23993-1-gnoack3000@gmail.com>
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Günther Noack, le mar. 08 août 2023 22:11:12 +0200, a ecrit:
> Clarifies that the LEGACY_TIOCSTI setting is safe to turn off even
> when running BRLTTY, as it was introduced in commit 690c8b804ad2
> ("TIOCSTI: always enable for CAP_SYS_ADMIN").
> 
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

> ---
>  drivers/tty/Kconfig | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index 341abaed4ce..069de553127 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -164,6 +164,9 @@ config LEGACY_TIOCSTI
>  	  userspace depends on this functionality to continue operating
>  	  normally.
>  
> +	  Processes which run with CAP_SYS_ADMIN, such as BRLTTY, can
> +	  use TIOCSTI even when this is set to N.
> +
>  	  This functionality can be changed at runtime with the
>  	  dev.tty.legacy_tiocsti sysctl. This configuration option sets
>  	  the default value of the sysctl.
> -- 
> 2.41.0
>