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Subject[PATCH v2 3/4] mm: replace pmd_write with pmd_access_permitted in fault + gup paths
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The 'access_permitted' helper is used in the gup-fast path and goes
beyond the simple _PAGE_RW check to also:

* validate that the mapping is writable from a protection keys
standpoint

* validate that the pte has _PAGE_USER set since all fault paths where
pmd_write is must be referencing user-memory.

Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
arch/sparc/mm/gup.c | 2 +-
fs/dax.c | 3 ++-
mm/hmm.c | 4 ++--
mm/huge_memory.c | 4 ++--
mm/memory.c | 2 +-
5 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index 5ae2d0a01a70..33c0f8bb0f33 100644
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/mm/gup.c
@@ -75,7 +75,7 @@ static int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
if (!(pmd_val(pmd) & _PAGE_VALID))
return 0;

- if (write && !pmd_write(pmd))
+ if (!pmd_access_permitted(pmd, write))
return 0;

refs = 0;
diff --git a/fs/dax.c b/fs/dax.c
index f001d8c72a06..3cc40eebbb9e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -620,7 +620,8 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,

if (pfn != pmd_pfn(*pmdp))
goto unlock_pmd;
- if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
+ if (!pmd_dirty(*pmdp)
+ && !pmd_access_permitted(*pmdp, WRITE))
goto unlock_pmd;

flush_cache_page(vma, address, pfn);
diff --git a/mm/hmm.c b/mm/hmm.c
index a88a847bccba..cbdd47bf6a48 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -391,11 +391,11 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
if (pmd_protnone(pmd))
return hmm_vma_walk_clear(start, end, walk);

- if (write_fault && !pmd_write(pmd))
+ if (!pmd_access_permitted(pmd, write_fault))
return hmm_vma_walk_clear(start, end, walk);

pfn = pmd_pfn(pmd) + pte_index(addr);
- flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
+ flag |= pmd_access_permitted(pmd, WRITE) ? HMM_PFN_WRITE : 0;
for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
pfns[i] = hmm_pfn_t_from_pfn(pfn) | flag;
return 0;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1e4e11275856..411ba3ba45f8 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -875,7 +875,7 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
*/
WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");

- if (flags & FOLL_WRITE && !pmd_write(*pmd))
+ if (!pmd_access_permitted(*pmd, flags & FOLL_WRITE))
return NULL;

if (pmd_present(*pmd) && pmd_devmap(*pmd))
@@ -1379,7 +1379,7 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
*/
static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
{
- return pmd_write(pmd) ||
+ return pmd_access_permitted(pmd, WRITE) ||
((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
}

diff --git a/mm/memory.c b/mm/memory.c
index 64f86beadcca..157fd4320bb3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4020,7 +4020,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
return do_huge_pmd_numa_page(&vmf, orig_pmd);

- if (dirty && !pmd_write(orig_pmd)) {
+ if (dirty && !pmd_access_permitted(orig_pmd, WRITE)) {
ret = wp_huge_pmd(&vmf, orig_pmd);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
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