Re: [Xen-devel] grant table interface addition?

To:	Jan Beulich <jbeulich@xxxxxxxxxx>
Subject:	Re: [Xen-devel] grant table interface addition?
From:	Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date:	Mon, 03 Nov 2008 12:55:47 +0000
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On 3/11/08 12:13, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> While looking in more detail into how all this fits together, I realized that
> there appears to be a race condition in blktap: Since fast_flush_area()
> and dispatch_rw_block_io() call create_lookup_pte_addr() without holding
> mm->mmap_sem, there's nothing preventing the just verified (or
> created) page table structures to go away again before
> HYPERVISOR_grant_table_op() is able to finish (or even begin) its job.
> Am I missing something here?

So, for example, it could be munmap()ed under those functions' feet? Or the
process could die? Looks like you could be right, although I've never looked
closely at the blktap kernel driver.

 -- Keir



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Re: [Xen-devel] grant table interface addition?