Re: [RFT][PATCH] mm: Fix race in kunmap_atomic()

[Rik van Riel]

On 10/27/2010 10:54 AM, Peter Zijlstra wrote:

> Christoph reported a nice splat which illustrated a race in the new
> stack based kmap_atomic implementation.
>
> The problem is that we pop our stack slot before we're completely done
> resetting its state -- in particular clearing the PTE (sometimes that's
> CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear
> the PTE used for the last slot, that interrupt can reuse the slot in a
> dirty state, which triggers a BUG in kmap_atomic().
>
> Fix this by introducing kmap_atomic_idx() which reports the current slot
> index without actually releasing it and use that to find the PTE and
> delay the _pop() until after we're completely done.
>
> Reported-by: Christoph Hellwig<hch@xxxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>

Acked-by: Rik van Riel <riel@xxxxxxxxxx>

--
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/