linux-kernel - [PATCH v2 2/4] mm: replace pud_write with pud_access

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Date:   Sat, 11 Nov 2017 12:11:44 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-nvdimm@...ts.01.org,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH v2 2/4] mm: replace pud_write with pud_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
  pud_write is must be referencing user-memory.

Cc: Dave Hansen <dave.hansen@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 arch/s390/include/asm/pgtable.h |    6 ++++++
 arch/sparc/mm/gup.c             |    2 +-
 mm/huge_memory.c                |    2 +-
 mm/memory.c                     |    2 +-
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index d7fe9838084d..1f36a01e22f6 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1264,6 +1264,12 @@ static inline pud_t pud_mkwrite(pud_t pud)
 	return pud;
 }
 
+#define __HAVE_ARCH_PUD_WRITE
+static inline int pud_write(pud_t pud)
+{
+	return (pud_val(pud) & _REGION3_ENTRY_WRITE) != 0;
+}
+
 static inline pud_t pud_mkclean(pud_t pud)
 {
 	if (pud_large(pud)) {
diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index 5335ba3c850e..5ae2d0a01a70 100644
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/mm/gup.c
@@ -114,7 +114,7 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
 	if (!(pud_val(pud) & _PAGE_VALID))
 		return 0;
 
-	if (write && !pud_write(pud))
+	if (!pud_access_permitted(pud, write))
 		return 0;
 
 	refs = 0;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1981ed697dab..1e4e11275856 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1022,7 +1022,7 @@ struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
 
 	assert_spin_locked(pud_lockptr(mm, pud));
 
-	if (flags & FOLL_WRITE && !pud_write(*pud))
+	if (!pud_access_permitted(*pud, flags & FOLL_WRITE))
 		return NULL;
 
 	if (pud_present(*pud) && pud_devmap(*pud))
diff --git a/mm/memory.c b/mm/memory.c
index a728bed16c20..64f86beadcca 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3987,7 +3987,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 
 			/* NUMA case for anonymous PUDs would go here */
 
-			if (dirty && !pud_write(orig_pud)) {
+			if (dirty && !pud_access_permitted(orig_pud, WRITE)) {
 				ret = wp_huge_pud(&vmf, orig_pud);
 				if (!(ret & VM_FAULT_FALLBACK))
 					return ret;