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authorAlistair Popple <apopple@nvidia.com>2022-09-28 22:01:17 +1000
committerAndrew Morton <akpm@linux-foundation.org>2022-10-12 18:51:49 -0700
commit0dc45ca1ce18900572282c4f054bbe78351cb6a7 (patch)
tree64a46a50d79e5eb66a74f1c6b0d56a45b846d199 /mm/memremap.c
parentef233450898f8893dafa193a9f3211fa077a3d05 (diff)
mm/memremap.c: take a pgmap reference on page allocation
ZONE_DEVICE pages have a struct dev_pagemap which is allocated by a driver. When the struct page is first allocated by the kernel in memremap_pages() a reference is taken on the associated pagemap to ensure it is not freed prior to the pages being freed. Prior to 27674ef6c73f ("mm: remove the extra ZONE_DEVICE struct page refcount") pages were considered free and returned to the driver when the reference count dropped to one. However the pagemap reference was not dropped until the page reference count hit zero. This would occur as part of the final put_page() in memunmap_pages() which would wait for all pages to be freed prior to returning. When the extra refcount was removed the pagemap reference was no longer being dropped in put_page(). Instead memunmap_pages() was changed to explicitly drop the pagemap references. This means that memunmap_pages() can complete even though pages are still mapped by the kernel which can lead to kernel crashes, particularly if a driver frees the pagemap. To fix this drivers should take a pagemap reference when allocating the page. This reference can then be returned when the page is freed. Link: https://lkml.kernel.org/r/12d155ec727935ebfbb4d639a03ab374917ea51b.1664366292.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Fixes: 27674ef6c73f ("mm: remove the extra ZONE_DEVICE struct page refcount") Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Felix Kuehling <Felix.Kuehling@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Christian König <christian.koenig@amd.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Lyude Paul <lyude@redhat.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Alex Sierra <alex.sierra@amd.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/memremap.c')
-rw-r--r--mm/memremap.c25
1 files changed, 19 insertions, 6 deletions
diff --git a/mm/memremap.c b/mm/memremap.c
index 1c2c038f3410..421bec3a29ee 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -138,8 +138,11 @@ void memunmap_pages(struct dev_pagemap *pgmap)
int i;
percpu_ref_kill(&pgmap->ref);
- for (i = 0; i < pgmap->nr_range; i++)
- percpu_ref_put_many(&pgmap->ref, pfn_len(pgmap, i));
+ if (pgmap->type != MEMORY_DEVICE_PRIVATE &&
+ pgmap->type != MEMORY_DEVICE_COHERENT)
+ for (i = 0; i < pgmap->nr_range; i++)
+ percpu_ref_put_many(&pgmap->ref, pfn_len(pgmap, i));
+
wait_for_completion(&pgmap->done);
for (i = 0; i < pgmap->nr_range; i++)
@@ -264,7 +267,9 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
PHYS_PFN(range->start),
PHYS_PFN(range_len(range)), pgmap);
- percpu_ref_get_many(&pgmap->ref, pfn_len(pgmap, range_id));
+ if (pgmap->type != MEMORY_DEVICE_PRIVATE &&
+ pgmap->type != MEMORY_DEVICE_COHERENT)
+ percpu_ref_get_many(&pgmap->ref, pfn_len(pgmap, range_id));
return 0;
err_add_memory:
@@ -502,16 +507,24 @@ void free_zone_device_page(struct page *page)
page->mapping = NULL;
page->pgmap->ops->page_free(page);
- /*
- * Reset the page count to 1 to prepare for handing out the page again.
- */
if (page->pgmap->type != MEMORY_DEVICE_PRIVATE &&
page->pgmap->type != MEMORY_DEVICE_COHERENT)
+ /*
+ * Reset the page count to 1 to prepare for handing out the page
+ * again.
+ */
set_page_count(page, 1);
+ else
+ put_dev_pagemap(page->pgmap);
}
void zone_device_page_init(struct page *page)
{
+ /*
+ * Drivers shouldn't be allocating pages after calling
+ * memunmap_pages().
+ */
+ WARN_ON_ONCE(!percpu_ref_tryget_live(&page->pgmap->ref));
set_page_count(page, 1);
lock_page(page);
}