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From:   Liam Howlett <liam.howlett@oracle.com>
To:     "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Yu Zhao <yuzhao@google.com>
Subject: [PATCH v8 58/70] mm/mlock: use vma iterator and instead of vma linked
 list
Thread-Topic: [PATCH v8 58/70] mm/mlock: use vma iterator and instead of vma
 linked list
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Date:   Tue, 26 Apr 2022 15:06:49 +0000
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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Handle overflow checking in count_mm_mlocked_page_nr() differently.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 mm/mlock.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index 716caf851043..d8549b3dcb59 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -471,6 +471,7 @@ static int apply_vma_lock_flags(unsigned long start, si=
ze_t len,
 	unsigned long nstart, end, tmp;
 	struct vm_area_struct *vma, *prev;
 	int error;
+	MA_STATE(mas, &current->mm->mm_mt, start, start);
=20
 	VM_BUG_ON(offset_in_page(start));
 	VM_BUG_ON(len !=3D PAGE_ALIGN(len));
@@ -479,13 +480,14 @@ static int apply_vma_lock_flags(unsigned long start, =
size_t len,
 		return -EINVAL;
 	if (end =3D=3D start)
 		return 0;
-	vma =3D find_vma(current->mm, start);
-	if (!vma || vma->vm_start > start)
+	vma =3D mas_walk(&mas);
+	if (!vma)
 		return -ENOMEM;
=20
-	prev =3D vma->vm_prev;
 	if (start > vma->vm_start)
 		prev =3D vma;
+	else
+		prev =3D mas_prev(&mas, 0);
=20
 	for (nstart =3D start ; ; ) {
 		vm_flags_t newflags =3D vma->vm_flags & VM_LOCKED_CLEAR_MASK;
@@ -505,7 +507,7 @@ static int apply_vma_lock_flags(unsigned long start, si=
ze_t len,
 		if (nstart >=3D end)
 			break;
=20
-		vma =3D prev->vm_next;
+		vma =3D find_vma(prev->vm_mm, prev->vm_end);
 		if (!vma || vma->vm_start !=3D nstart) {
 			error =3D -ENOMEM;
 			break;
@@ -526,24 +528,23 @@ static unsigned long count_mm_mlocked_page_nr(struct =
mm_struct *mm,
 {
 	struct vm_area_struct *vma;
 	unsigned long count =3D 0;
+	unsigned long end;
+	VMA_ITERATOR(vmi, mm, start);
=20
 	if (mm =3D=3D NULL)
 		mm =3D current->mm;
=20
-	vma =3D find_vma(mm, start);
-	if (vma =3D=3D NULL)
-		return 0;
-
-	for (; vma ; vma =3D vma->vm_next) {
-		if (start >=3D vma->vm_end)
-			continue;
-		if (start + len <=3D  vma->vm_start)
-			break;
+	/* Don't overflow past ULONG_MAX */
+	if (unlikely(ULONG_MAX - len < start))
+		end =3D ULONG_MAX;
+	else
+		end =3D start + len;
+	for_each_vma_range(vmi, vma, end) {
 		if (vma->vm_flags & VM_LOCKED) {
 			if (start > vma->vm_start)
 				count -=3D (start - vma->vm_start);
-			if (start + len < vma->vm_end) {
-				count +=3D start + len - vma->vm_start;
+			if (end < vma->vm_end) {
+				count +=3D end - vma->vm_start;
 				break;
 			}
 			count +=3D vma->vm_end - vma->vm_start;
@@ -659,6 +660,7 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, =
len)
  */
 static int apply_mlockall_flags(int flags)
 {
+	VMA_ITERATOR(vmi, current->mm, 0);
 	struct vm_area_struct *vma, *prev =3D NULL;
 	vm_flags_t to_add =3D 0;
=20
@@ -679,7 +681,7 @@ static int apply_mlockall_flags(int flags)
 			to_add |=3D VM_LOCKONFAULT;
 	}
=20
-	for (vma =3D current->mm->mmap; vma ; vma =3D prev->vm_next) {
+	for_each_vma(vmi, vma) {
 		vm_flags_t newflags;
=20
 		newflags =3D vma->vm_flags & VM_LOCKED_CLEAR_MASK;
--=20
2.35.1