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DateTue, 06 Aug 2002 11:42:49 +0200
FromManfred Spraul <>
SubjectRe: [TRIVIAL] Warn users about machines with non-working WP bit
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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