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Date:   Mon, 13 Nov 2023 13:33:48 -0500
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Tomas Mudrunka <tomas.mudrunka@gmail.com>
Cc:     Jiri Slaby <jirislaby@kernel.org>, linux-kernel@vger.kernel.org,
        linux-serial@vger.kernel.org
Subject: Re: [PATCH] /proc/sysrq-trigger: accept multiple keys at once
Message-ID: <2023111333-duly-mobility-edc7@gregkh>
References: <20231113182227.698989-1-tomas.mudrunka@gmail.com>
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On Mon, Nov 13, 2023 at 07:22:19PM +0100, Tomas Mudrunka wrote:
> Just for convenience.
> This way we can do:
> `echo reisub > /proc/sysrq-trigger`
> Instead of:
> `for i in r e i s u b; do echo "$i" > /proc/sysrq-trigger; done;`
> 
> Signed-off-by: Tomas Mudrunka <tomas.mudrunka@gmail.com>
> ---
>  drivers/tty/sysrq.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 6b4a28bcf..bc5a679f6 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -1154,10 +1154,12 @@ EXPORT_SYMBOL(unregister_sysrq_key);
>  static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
>  				   size_t count, loff_t *ppos)
>  {
> -	if (count) {
> +	size_t i;
> +
> +	for (i = 0; i < count; i++) {
>  		char c;
>  
> -		if (get_user(c, buf))
> +		if (get_user(c, buf+i))

What did you just break where people would send a string and only relied
on the first character being checked?  This might not be ok to do.

Also, no documentation update?

thanks,

greg k-h