From 60081bf19b0ec8fa40c589bd361fa2bc763f1050 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Fri, 4 Aug 2023 08:27:22 -0700 Subject: mm: lock vma explicitly before doing vm_flags_reset and vm_flags_reset_once Implicit vma locking inside vm_flags_reset() and vm_flags_reset_once() is not obvious and makes it hard to understand where vma locking is happening. Also in some cases (like in dup_userfaultfd()) vma should be locked earlier than vma_flags modification. To make locking more visible, change these functions to assert that the vma write lock is taken and explicitly lock the vma beforehand. Fix userfaultfd functions which should lock the vma earlier. Link: https://lkml.kernel.org/r/20230804152724.3090321-5-surenb@google.com Suggested-by: Linus Torvalds Signed-off-by: Suren Baghdasaryan Cc: Jann Horn Cc: Liam R. Howlett Signed-off-by: Andrew Morton --- mm/mlock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 0a0c996c5c21..1746600a2e14 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -386,6 +386,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, */ if (newflags & VM_LOCKED) newflags |= VM_IO; + vma_start_write(vma); vm_flags_reset_once(vma, newflags); lru_add_drain(); @@ -460,9 +461,9 @@ success: * 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 ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) { /* No work to do, and mlocking twice would be wrong */ + vma_start_write(vma); vm_flags_reset(vma, newflags); } else { mlock_vma_pages_range(vma, start, end, newflags); -- cgit v1.2.3