From: Suren Baghdasaryan <surenb@google.com>
Date: Thu, 7 Jul 2022 23:16:34 +0000 (-0700)
Subject: mm/mmap: write-lock adjacent VMAs if they can grow into unmapped area
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d8ae22ca901ec283b5d2c1fb670c3c2acd181538;p=users%2Fjedix%2Flinux-maple.git

mm/mmap: write-lock adjacent VMAs if they can grow into unmapped area

While unmapping VMAs, adjacent VMAs might be able to grow into the area
being unmapped. In such cases write-lock adjacent VMAs to prevent this
growth.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index faa5d3a5d45b..50f6494d2178 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2461,11 +2461,13 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 	 * down_read(mmap_lock) and collide with the VMA we are about to unmap.
 	 */
 	if (downgrade) {
-		if (next && (next->vm_flags & VM_GROWSDOWN))
+		if (next && (next->vm_flags & VM_GROWSDOWN)) {
+			vma_write_lock(next);
 			downgrade = false;
-		else if (prev && (prev->vm_flags & VM_GROWSUP))
+		} else if (prev && (prev->vm_flags & VM_GROWSUP)) {
+			vma_write_lock(prev);
 			downgrade = false;
-		else
+		} else
 			mmap_write_downgrade(mm);
 	}