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

On Sat 30-03-19 11:11:21, Aneesh Kumar K.V wrote:

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

Thanks for fixing this! The patch looks good to me. Feel free to add:

Reviewed-by: Jan Kara jack@suse.cz

Honza

---

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