[RFC v3 12/17] mm/spf: Protect changes to vm_flags

[Laurent Dufour]

Protect VMA's flags change against the speculative page fault handler.

Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
 fs/proc/task_mmu.c | 2 ++
 mm/mempolicy.c     | 2 ++
 mm/mlock.c         | 9 ++++++---
 mm/mmap.c          | 2 ++
 mm/mprotect.c      | 2 ++
 5 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8f96a49178d0..54c9a87530cb 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1055,8 +1055,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 					goto out_mm;
 				}
 				for (vma = mm->mmap; vma; vma = vma->vm_next) {
+					write_seqcount_begin(&vma->vm_sequence);
 					vma->vm_flags &= ~VM_SOFTDIRTY;
 					vma_set_page_prot(vma);
+					write_seqcount_end(&vma->vm_sequence);
 				}
 				downgrade_write(&mm->mmap_sem);
 				break;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 1e7873e40c9a..1518b022927d 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -603,9 +603,11 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
 {
 	int nr_updated;
 
+	write_seqcount_begin(&vma->vm_sequence);
 	nr_updated = change_protection(vma, addr, end, PAGE_NONE, 0, 1);
 	if (nr_updated)
 		count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated);
+	write_seqcount_end(&vma->vm_sequence);
 
 	return nr_updated;
 }
diff --git a/mm/mlock.c b/mm/mlock.c
index cdbed8aaa426..44cf70413530 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -437,7 +437,9 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
 void munlock_vma_pages_range(struct vm_area_struct *vma,
 			     unsigned long start, unsigned long end)
 {
+	write_seqcount_begin(&vma->vm_sequence);
 	vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+	write_seqcount_end(&vma->vm_sequence);
 
 	while (start < end) {
 		struct page *page;
@@ -563,10 +565,11 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 	 * It's okay if try_to_unmap_one unmaps a page just after we
 	 * set VM_LOCKED, populate_vma_page_range will bring it back.
 	 */
-
-	if (lock)
+	if (lock) {
+		write_seqcount_begin(&vma->vm_sequence);
 		vma->vm_flags = newflags;
-	else
+		write_seqcount_end(&vma->vm_sequence);
+	} else
 		munlock_vma_pages_range(vma, start, end);
 
 out:
diff --git a/mm/mmap.c b/mm/mmap.c
index 27f407d8f7d7..815065d740c4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1742,6 +1742,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 out:
 	perf_event_mmap(vma);
 
+	write_seqcount_begin(&vma->vm_sequence);
 	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
 		if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
@@ -1764,6 +1765,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	vma->vm_flags |= VM_SOFTDIRTY;
 
 	vma_set_page_prot(vma);
+	write_seqcount_end(&vma->vm_sequence);
 
 	return addr;
 
diff --git a/mm/mprotect.c b/mm/mprotect.c
index f9c07f54dd62..646347faf4d5 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -341,6 +341,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 	 * vm_flags and vm_page_prot are protected by the mmap_sem
 	 * held in write mode.
 	 */
+	write_seqcount_begin(&vma->vm_sequence);
 	vma->vm_flags = newflags;
 	dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);
 	vma_set_page_prot(vma);
@@ -356,6 +357,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 			(newflags & VM_WRITE)) {
 		populate_vma_page_range(vma, start, end, NULL);
 	}
+	write_seqcount_end(&vma->vm_sequence);
 
 	vm_stat_account(mm, oldflags, -nrpages);
 	vm_stat_account(mm, newflags, nrpages);
-- 
2.7.4