diff mbox series

[25/41] mm/mmap: write-lock adjacent VMAs if they can grow into unmapped area

Message ID 20230109205336.3665937-26-surenb@google.com
State New
Headers
Series Per-VMA locks |

Commit Message

Suren Baghdasaryan Jan. 9, 2023, 8:53 p.m. UTC 
  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>
---
 mm/mmap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/mm/mmap.c b/mm/mmap.c
index 0d767ce043af..30c7d1c5206e 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);
 	}