[PATCH AUTOSEL 5.6 139/149] powerpc/book3s64: Fix error handling in mm_iommu_do_alloc()

Sasha Levin
2020-04-11T23:06:53Z

From: Alexey Kardashevskiy <aik@ozlabs.ru>

[ Upstream commit c4b78169e3667413184c9a20e11b5832288a109f ]

The last jump to free_exit in mm_iommu_do_alloc() happens after page
pointers in struct mm_iommu_table_group_mem_t were already converted to
physical addresses. Thus calling put_page() on these physical addresses
will likely crash.

This moves the loop which calculates the pageshift and converts page
struct pointers to physical addresses later after the point when
we cannot fail; thus eliminating the need to convert pointers back.

Fixes: eb9d7a62c386 ("powerpc/mm_iommu: Fix potential deadlock")
Reported-by: Jan Kara <jack@suse.cz>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191223060351.26359-1-aik@ozlabs.ru
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/mm/book3s64/iommu_api.c | 39 +++++++++++++++-------------
1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
index eba73ebd8ae57..fa05bbd1f6829 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -121,24 +121,6 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
goto free_exit;
}

- pageshift = PAGE_SHIFT;
- for (i = 0; i < entries; ++i) {
- struct page *page = mem->hpages[i];
-
- /*
- * Allow to use larger than 64k IOMMU pages. Only do that
- * if we are backed by hugetlb.
- */
- if ((mem->pageshift > PAGE_SHIFT) && PageHuge(page))
- pageshift = page_shift(compound_head(page));
- mem->pageshift = min(mem->pageshift, pageshift);
- /*
- * We don't need struct page reference any more, switch
- * to physical address.
- */
- mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT;
- }
-
good_exit:
atomic64_set(&mem->mapped, 1);
mem->used = 1;
@@ -158,6 +140,27 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
}
}

+ if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
+ /*
+ * Allow to use larger than 64k IOMMU pages. Only do that
+ * if we are backed by hugetlb. Skip device memory as it is not
+ * backed with page structs.
+ */
+ pageshift = PAGE_SHIFT;
+ for (i = 0; i < entries; ++i) {
+ struct page *page = mem->hpages[i];
+
+ if ((mem->pageshift > PAGE_SHIFT) && PageHuge(page))
+ pageshift = page_shift(compound_head(page));
+ mem->pageshift = min(mem->pageshift, pageshift);
+ /*
+ * We don't need struct page reference any more, switch
+ * to physical address.
+ */
+ mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT;
+ }
+ }
+
list_add_rcu(&mem->next, &mm->context.iommu_group_mem_list);

mutex_unlock(&mem_list_mutex);
--
2.20.1