From: Dan Williams <dan.j.williams@xxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reported-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reported-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Xiong Zhou <xzhou@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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;
}
_