diff options
| author | Gerald Schaefer <gerald.schaefer@de.ibm.com> | 2017-09-18 16:51:51 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-09-19 08:36:20 +0200 |
| commit | ba385c0594e723d41790ecfb12c610e6f90c7785 (patch) | |
| tree | da82a51857fa5ee45e492b945120889714d78840 /arch/s390 | |
| parent | 91c575b335766effa6103eba42a82aea560c365f (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.c | 7 |
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)); |