Re: [PATCH] off-by-1 in kernel/power/main.c

[Pavel Machek <pavel@ucw.cz>]

Hi!

> there's an off-by-1 in 2.6.16.9 (and 2.6.17-rc2) 
> kernel/power/main.c:state_store() ... if your kernel just happens to have 
> some non-zero data at pm_states[PM_SUSPEND_MAX] (i.e. one past the end of 
> the array) then it'll let you write anything you want to /sys/power/state 
> and in response the box will enter S5.
> 
> i randomly discovered this because i really wanted to put my box into S5 
> (for wake on lan) and tried "echo off >/sys/power/state" and was quite 
> happy that the box entered S5... happy until i compiled a different kernel 
> and this S5 trick stopped working :)
> 
> anyhow, this begs the question, what is the correct way to get a box to 
> shutdown into s5?  on a fc4 box i have here it does that happily, but 
> ubuntu boxes don't seem to go into s5... and i couldn't figure out from 
> fc4 patches if they'd changed anything in this area.  pointers 
> appreciated.
> 
> btw i can whip up a patch making "off" a valid value for /sys/power/state 
> ...

Looks okay to me. Can you add acked-by: Pavel Machek and mail it to
akpm?

Valid way to power off machine is by shutdown -o now, and there's a
syscall to do that. It should not be done by /sys/power/state.

								Pavel

-- 
Thanks for all the (sleeping) penguins.