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);