On Fri, 2018-07-27 at 11:48:17 UTC, Nicholas Piggin wrote:
> The page table fragment allocator uses the main page refcount racily
> with respect to speculative references. A customer observed a BUG due
> to page table page refcount underflow in the fragment allocator. This
> can be caused by the fragment allocator set_page_count stomping on a
> speculative reference, and then the speculative failure handler
> decrements the new reference, and the underflow eventually pops when
> the page tables are freed.
>
> Fix this by using a dedicated field in the struct page for the page
> table fragment allocator.
>
> Fixes: 5c1f6ee9a31c ("powerpc: Reduce PTE table memory wastage")
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/4231aba000f5a4583dd9f67057aadb
cheers
