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

From: Manfred Spraul (manfred@colorfullife.com)
Date: Tue Aug 06 2002 - 04:42:49 EST

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David S. Miller wrote:

> 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.
>
>
Then we should either fix copy_to_user(), or mark 80386 unsupported, or
disable multi-threading on 80386. It's a random memory corruption, far
worse than a security hole.

-- Manfred

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