# Re: \[PATCH RFC 19/23\] tty: sysrq: let procfs copy in writes to /proc/sysrq-trigger

- From: Jiri Slaby \<jirislaby@kernel.org\>
- Date: 2026-11-03 06:54:35 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2026/11/17849892
- Thread: https://ratatoskr.run/linux-fsdevel/2026/11/17844895/t/3.md

```text
On 02. 11. 26, 16:07, Christian Brauner wrote:
> Implement ->proc_write_buf() so procfs copies in what is written before
> it pins the entry, and handle the keys from that copy. Writes larger
> than PAGE_SIZE - 1 bytes fail with -EINVAL now. They used to trigger the
> first key, or all of them in bulk mode. procfs allocates the copy, which
> is as small as the write, opening the file allocated as much already.
>
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>

> ---
>   drivers/tty/sysrq.c | 9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index f4571d05b496..99363e1b59ed 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -1200,17 +1200,14 @@ EXPORT_SYMBOL(unregister_sysrq_key);
>    * However, if the first character is an underscore,
>    * all characters are processed.
>    */
> -static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
> +static ssize_t write_sysrq_trigger(struct file *file, char *buf,
>   				   size_t count, loff_t *ppos)
>   {
>   	bool bulk = false;
>   	size_t i;
>   
>   	for (i = 0; i < count; i++) {
> -		char c;
> -
> -		if (get_user(c, buf + i))
> -			return -EFAULT;
> +		char c = buf[i];
>   
>   		if (c == '_')
>   			bulk = true;
> @@ -1225,7 +1222,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
>   }
>   
>   static const struct proc_ops sysrq_trigger_proc_ops = {
> -	.proc_write	= write_sysrq_trigger,
> +	.proc_write_buf	= write_sysrq_trigger,
>   	.proc_lseek	= noop_llseek,
>   };
>   
>


-- 
js
suse labs

```