linux-kernel - [PATCH v2 4/4] mm: replace pte_write with pte_access

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Date:   Sat, 11 Nov 2017 12:11:56 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Dave Hansen <dave.hansen@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH v2 4/4] mm: replace pte_write with pte_access_permitted in
 fault + gup paths

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
  pte_write is must be referencing user-memory.

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

diff --git a/mm/gup.c b/mm/gup.c
index b2b4d4263768..bb6542c47b08 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -66,7 +66,7 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
  */
 static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
 {
-	return pte_write(pte) ||
+	return pte_access_permitted(pte, WRITE) ||
 		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
 }
 
diff --git a/mm/hmm.c b/mm/hmm.c
index cbdd47bf6a48..3d2e49fd851a 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -456,11 +456,11 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
 			continue;
 		}
 
-		if (write_fault && !pte_write(pte))
+		if (!pte_access_permitted(pte, write_fault))
 			goto fault;
 
 		pfns[i] = hmm_pfn_t_from_pfn(pte_pfn(pte)) | flag;
-		pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
+		pfns[i] |= pte_access_permitted(pte, WRITE) ? HMM_PFN_WRITE : 0;
 		continue;
 
 fault:
diff --git a/mm/memory.c b/mm/memory.c
index 157fd4320bb3..a8cbc2c3e3c9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3922,7 +3922,7 @@ static int handle_pte_fault(struct vm_fault *vmf)
 	if (unlikely(!pte_same(*vmf->pte, entry)))
 		goto unlock;
 	if (vmf->flags & FAULT_FLAG_WRITE) {
-		if (!pte_write(entry))
+		if (!pte_access_permitted(entry, WRITE))
 			return do_wp_page(vmf);
 		entry = pte_mkdirty(entry);
 	}
@@ -4308,7 +4308,7 @@ int follow_phys(struct vm_area_struct *vma,
 		goto out;
 	pte = *ptep;
 
-	if ((flags & FOLL_WRITE) && !pte_write(pte))
+	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
 		goto unlock;
 
 	*prot = pgprot_val(pte_pgprot(pte));