From 9ed858e47c3938fdff8c22fb386bdc3366773093 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Wed, 27 Apr 2022 11:13:03 -0400 Subject: [PATCH] fs/userfaultfd: Fix maple state in userfaultfd_register() When VMAs are split/merged, the maple tree node may be replaced. Re-walk the tree in such cases by calling mas_pause(). Signed-off-by: Liam R. Howlett --- fs/userfaultfd.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index bb7338391b2c..974e04c51954 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1437,6 +1437,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, ((struct vm_userfaultfd_ctx){ ctx }), anon_vma_name(vma)); if (prev) { + /* vma_merge() invalidated the mas */ + mas_pause(&mas); vma = prev; goto next; } @@ -1444,11 +1446,15 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, ret = split_vma(mm, vma, start, 1); if (ret) break; + /* split_vma() invalidated the mas */ + mas_pause(&mas); } if (vma->vm_end > end) { ret = split_vma(mm, vma, end, 0); if (ret) break; + /* split_vma() invalidated the mas */ + mas_pause(&mas); } next: /* -- 2.35.1