Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline

Jiri Kosina
2014-04-02T23:57:56Z

On Wed, 2 Apr 2014, Linus Torvalds wrote:

> > Which doesn't really protect you from tasks that do open()/write()/close()
> > cycle for /dev/kmsg write every 2ms though.
>
> I don't think we should try to protect against wilful bad behavior
> unless that is shown to be necessary. Yeah, if it turns out that
> systemd really does that just to mess with us, we'd need to extend it,
> but in the absence of proof to the contrary, maybe this simple
> attached patch works?
>
> TOTALLY UNTESTED. But it really isn't complex.

[ ... snip ... [
@@ -483,6 +484,8 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,

if (!user)
return -EBADF;
+ if (!___ratelimit(&user->rs, current->comm))
+ return 0;

I am admittedly rather new to this 'abuse the hell out of kernel
ringbuffer' thing, but shouldn't we better be limiting the
devkmsg_writev()?

--
Jiri Kosina
SUSE Labs