+ x86-mm-fix-gup_pte_range-vs-dax-mappings.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: x86, mm: fix gup_pte_range() vs DAX mappings
has been added to the -mm tree.  Its filename is
     x86-mm-fix-gup_pte_range-vs-dax-mappings.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/x86-mm-fix-gup_pte_range-vs-dax-mappings.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/x86-mm-fix-gup_pte_range-vs-dax-mappings.patch

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------------------------------------------------------
From: Dan Williams <dan.j.williams@intel.com>
Subject: x86, mm: fix gup_pte_range() vs DAX mappings

gup_pte_range() fails to check pte_allows_gup() before translating a DAX
pte entry, pte_devmap(), to a page.  This allows writes to read-only
mappings, and bypasses the DAX cacheline dirty tracking due to missed
'mkwrite' faults.  The gup_huge_pmd() path and the gup_huge_pud() path
correctly check pte_allows_gup() before checking for _devmap() entries.

Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Link: http://lkml.kernel.org/r/148804251312.36605.12665024794196605053.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Dave Hansen <dave.hansen@linux.intel.com>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Xiong Zhou <xzhou@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/mm/gup.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff -puN arch/x86/mm/gup.c~x86-mm-fix-gup_pte_range-vs-dax-mappings arch/x86/mm/gup.c
--- a/arch/x86/mm/gup.c~x86-mm-fix-gup_pte_range-vs-dax-mappings
+++ a/arch/x86/mm/gup.c
@@ -120,6 +120,11 @@ static noinline int gup_pte_range(pmd_t
 			return 0;
 		}
 
+		if (!pte_allows_gup(pte_val(pte), write)) {
+			pte_unmap(ptep);
+			return 0;
+		}
+
 		if (pte_devmap(pte)) {
 			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
 			if (unlikely(!pgmap)) {
@@ -127,8 +132,7 @@ static noinline int gup_pte_range(pmd_t
 				pte_unmap(ptep);
 				return 0;
 			}
-		} else if (!pte_allows_gup(pte_val(pte), write) ||
-			   pte_special(pte)) {
+		} else if (pte_special(pte)) {
 			pte_unmap(ptep);
 			return 0;
 		}
_

Patches currently in -mm which might be from dan.j.williams@intel.com are

x86-mm-fix-gup_pte_range-vs-dax-mappings.patch
x86-mm-unify-exit-paths-in-gup_pte_range.patch