[PATCH] mm: Fix modifying of page protection by insert_pfn_pmd()

Aneesh Kumar K.V
2019-03-30T05:41:37Z

With some architectures like ppc64, set_pmd_at() cannot cope with
a situation where there is already some (different) valid entry present.

Use pmdp_set_access_flags() instead to modify the pfn which is built to
deal with modifying existing PMD entries.

This is similar to
commit cae85cb8add3 ("mm/memory.c: fix modifying of page protection by insert_pfn()")

We also do similar update w.r.t insert_pfn_pud eventhough ppc64 don't support
pud pfn entries now.

CC: stable@vger.kernel.org
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
mm/huge_memory.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 404acdcd0455..f7dca413c4b2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -755,6 +755,20 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
spinlock_t *ptl;

ptl = pmd_lock(mm, pmd);
+ if (!pmd_none(*pmd)) {
+ if (write) {
+ if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
+ WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
+ goto out_unlock;
+ }
+ entry = pmd_mkyoung(*pmd);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
+ update_mmu_cache_pmd(vma, addr, pmd);
+ }
+ goto out_unlock;
+ }
+
entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pmd_mkdevmap(entry);
@@ -770,6 +784,7 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,

set_pmd_at(mm, addr, pmd, entry);
update_mmu_cache_pmd(vma, addr, pmd);
+out_unlock:
spin_unlock(ptl);
}

@@ -821,6 +836,20 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
spinlock_t *ptl;

ptl = pud_lock(mm, pud);
+ if (!pud_none(*pud)) {
+ if (write) {
+ if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
+ WARN_ON_ONCE(!is_huge_zero_pud(*pud));
+ goto out_unlock;
+ }
+ entry = pud_mkyoung(*pud);
+ entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
+ if (pudp_set_access_flags(vma, addr, pud, entry, 1))
+ update_mmu_cache_pud(vma, addr, pud);
+ }
+ goto out_unlock;
+ }
+
entry = pud_mkhuge(pfn_t_pud(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pud_mkdevmap(entry);
@@ -830,6 +859,8 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
}
set_pud_at(mm, addr, pud, entry);
update_mmu_cache_pud(vma, addr, pud);
+
+out_unlock:
spin_unlock(ptl);
}

--
2.20.1