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

From: David S. Miller (
Date: Tue Aug 06 2002 - 04:28:13 EST

   From: Manfred Spraul <>
   Date: Tue, 06 Aug 2002 11:17:33 +0200

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