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| author | Gerald Schaefer <gerald.schaefer@de.ibm.com> | 2017-09-18 17:51:51 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-05 10:44:01 +0300 |
| commit | 22338c55658d888326bd1998f8d4328c76809053 (patch) | |
| tree | 6f93e60d9361973dd87165ede3caaaed4593e32c /arch/s390/mm | |
| parent | c76655fb0f448de4cfadc83d3266c05a0a3c5dc0 (diff) | |
| download | linux-22338c55658d888326bd1998f8d4328c76809053.tar.xz | |
s390/mm: fix write access check in gup_huge_pmd()
commit ba385c0594e723d41790ecfb12c610e6f90c7785 upstream.
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.
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/s390/mm')
| -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 18d4107e10ee..97fc449a7470 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)); |