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SubjectRe: [PATCH] mm/hmm: Fix bad subpage pointer in try_to_unmap_one
On Tue, 9 Jul 2019 18:24:57 -0700 Ralph Campbell <rcampbell@nvidia.com> wrote:

>
> On 7/9/19 5:28 PM, Andrew Morton wrote:
> > On Tue, 9 Jul 2019 15:35:56 -0700 Ralph Campbell <rcampbell@nvidia.com> wrote:
> >
> >> When migrating a ZONE device private page from device memory to system
> >> memory, the subpage pointer is initialized from a swap pte which computes
> >> an invalid page pointer. A kernel panic results such as:
> >>
> >> BUG: unable to handle page fault for address: ffffea1fffffffc8
> >>
> >> Initialize subpage correctly before calling page_remove_rmap().
> >
> > I think this is
> >
> > Fixes: a5430dda8a3a1c ("mm/migrate: support un-addressable ZONE_DEVICE page in migration")
> > Cc: stable
> >
> > yes?
> >
>
> Yes. Can you add this or should I send a v2?

I updated the patch. Could we please have some review input?


From: Ralph Campbell <rcampbell@nvidia.com>
Subject: mm/hmm: fix bad subpage pointer in try_to_unmap_one

When migrating a ZONE device private page from device memory to system
memory, the subpage pointer is initialized from a swap pte which computes
an invalid page pointer. A kernel panic results such as:

BUG: unable to handle page fault for address: ffffea1fffffffc8

Initialize subpage correctly before calling page_remove_rmap().

Link: http://lkml.kernel.org/r/20190709223556.28908-1-rcampbell@nvidia.com
Fixes: a5430dda8a3a1c ("mm/migrate: support un-addressable ZONE_DEVICE page in migration")
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/rmap.c | 1 +
1 file changed, 1 insertion(+)

--- a/mm/rmap.c~mm-hmm-fix-bad-subpage-pointer-in-try_to_unmap_one
+++ a/mm/rmap.c
@@ -1476,6 +1476,7 @@ static bool try_to_unmap_one(struct page
* No need to invalidate here it will synchronize on
* against the special swap migration pte.
*/
+ subpage = page;
goto discard;
}

_
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