Re: [Xen-devel] [PATCH V2] xen: avoid race in p2m handling

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 17/10/14 12:16, Juergen Gross wrote:
> When a new p2m leaf is allocated this leaf is linked into the p2m tree
> via cmpxchg. Unfortunately the compare value for checking the success
> of the update is read after checking for the need of a new leaf. It is
> possible that a new leaf has been linked into the tree concurrently
> in between. This could lead to a leaked memory page and to the loss of
> some p2m entries.
> 
> Avoid the race by using the read compare value for checking the need
> of a new p2m leaf and use ACCESS_ONCE() to get it.
> 
> There are other places which seem to need ACCESS_ONCE() to ensure
> proper operation. Change them accordingly.

Applied, thanks.

David

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