linux-kernel - [PATCH v6 59/71] mm/mlock: Use vma iterator and instead of vma linked list

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Message-ID: <20220215144241.3812052-59-Liam.Howlett@oracle.com>
Date:   Tue, 15 Feb 2022 14:43:25 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v6 59/71] mm/mlock: Use vma iterator and instead of vma linked
 list

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

Handle overflow checking in count_mm_mlocked_page_nr() differently.

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

diff --git a/mm/mlock.c b/mm/mlock.c
index 8f584eddd305..8d54f355080f 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -563,6 +563,7 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
 	unsigned long nstart, end, tmp;
 	struct vm_area_struct *vma, *prev;
 	int error;
+	MA_STATE(mas, &current->mm->mm_mt, start, start);
 
 	VM_BUG_ON(offset_in_page(start));
 	VM_BUG_ON(len != PAGE_ALIGN(len));
@@ -571,13 +572,14 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
 		return -EINVAL;
 	if (end == start)
 		return 0;
-	vma = find_vma(current->mm, start);
-	if (!vma || vma->vm_start > start)
+	vma = mas_walk(&mas);
+	if (!vma)
 		return -ENOMEM;
 
-	prev = vma->vm_prev;
 	if (start > vma->vm_start)
 		prev = vma;
+	else
+		prev = mas_prev(&mas, 0);
 
 	for (nstart = start ; ; ) {
 		vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
@@ -597,7 +599,7 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
 		if (nstart >= end)
 			break;
 
-		vma = prev->vm_next;
+		vma = find_vma(prev->vm_mm, prev->vm_end);
 		if (!vma || vma->vm_start != nstart) {
 			error = -ENOMEM;
 			break;
@@ -618,24 +620,23 @@ static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
 {
 	struct vm_area_struct *vma;
 	unsigned long count = 0;
+	unsigned long end;
+	VMA_ITERATOR(vmi, mm, start);
 
 	if (mm == NULL)
 		mm = current->mm;
 
-	vma = find_vma(mm, start);
-	if (vma == NULL)
-		return 0;
-
-	for (; vma ; vma = vma->vm_next) {
-		if (start >= vma->vm_end)
-			continue;
-		if (start + len <=  vma->vm_start)
-			break;
+	/* Don't overflow past ULONG_MAX */
+	if (unlikely(ULONG_MAX - len < start))
+		end = ULONG_MAX;
+	else
+		end = start + len;
+	for_each_vma_range(vmi, vma, end) {
 		if (vma->vm_flags & VM_LOCKED) {
 			if (start > vma->vm_start)
 				count -= (start - vma->vm_start);
-			if (start + len < vma->vm_end) {
-				count += start + len - vma->vm_start;
+			if (end < vma->vm_end) {
+				count += end - vma->vm_start;
 				break;
 			}
 			count += vma->vm_end - vma->vm_start;
@@ -739,6 +740,7 @@ 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 = NULL;
 	vm_flags_t to_add = 0;
 
@@ -759,7 +761,7 @@ static int apply_mlockall_flags(int flags)
 			to_add |= VM_LOCKONFAULT;
 	}
 
-	for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
+	for_each_vma(vmi, vma) {
 		vm_flags_t newflags;
 
 		newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
-- 
2.34.1