Re: [TRIVIAL] Warn users about machines with non-working WP bit

David S. Miller
2002-08-06T09:37:17Z

From: Manfred Spraul <manfred@colorfullife.com>
Date: Tue, 06 Aug 2002 11:17:33 +0200

> - printk("No.\n");
> + printk("No (that's security hole).\n");
> #ifdef CONFIG_X86_WP_WORKS_OK

Could you explain the hole?
WP works for user space apps, only ring0 (or ring 0-2?) code
ignores the WP bit on i386.

So copy_to_user() could write to user areas that are write-proteced.

verify_area() checks aren't enough, consider a threaded application
calling mprotect() while the copy is in progress.