Messages in this thread | | | Date | Tue, 06 Aug 2002 16:36:35 +0200 | From | Manfred Spraul <> | Subject | Re: [TRIVIAL] Warn users about machines with non-working WP bit |
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Kasper Dupont wrote:
>I just get another idea, that might be easier to get right. If >the only problem is one process changing the mm while another >process is doing a copy_to_user, we should be able to fix it by >placing a readlock on the mm while the copy_to_user is in progress. > > Yes, that would work. copy_to_user is never called with the mmap semaphore locked, i.e.
#define copy_to_user(...) \ down(¤t->mm->mmap_sem); \ check_wp_bit(); \ real_copy_to_user(); \ up(¤t->mm->mmap_sem)
verify_area would just check that the pointer is below TASK_SIZE, and the wp bit is checked within copy_to_user().
But how many 80386 Linux systems that run the 2.4 kernel exist?
-- Manfred
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