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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2017-09-18 16:51:51 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-09-19 08:36:20 +0200
commitba385c0594e723d41790ecfb12c610e6f90c7785 (patch)
treeda82a51857fa5ee45e492b945120889714d78840 /arch/s390
parent91c575b335766effa6103eba42a82aea560c365f (diff)
s390/mm: fix write access check in gup_huge_pmd()
The check for the _SEGMENT_ENTRY_PROTECT bit in gup_huge_pmd() is the wrong way around. It must not be set for write==1, and not be checked for write==0. Fix this similar to how it was fixed for ptes long time ago in commit 25591b070336 ("[S390] fix get_user_pages_fast"). One impact of this bug would be unnecessarily using the gup slow path for write==0 on r/w mappings. A potentially more severe impact would be that gup_huge_pmd() will succeed for write==1 on r/o mappings. Cc: <stable@vger.kernel.org> Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/mm/gup.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 8ecc25e760fa..98ffe3ee9411 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -56,13 +56,12 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
- unsigned long mask, result;
struct page *head, *page;
+ unsigned long mask;
int refs;
- result = write ? 0 : _SEGMENT_ENTRY_PROTECT;
- mask = result | _SEGMENT_ENTRY_INVALID;
- if ((pmd_val(pmd) & mask) != result)
+ mask = (write ? _SEGMENT_ENTRY_PROTECT : 0) | _SEGMENT_ENTRY_INVALID;
+ if ((pmd_val(pmd) & mask) != 0)
return 0;
VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT));