[Devel] [PATCH vz8 04/42] fs/userfaultfd.c: wp: clear VM_UFFD_MISSING or VM_UFFD_WP during userfaultfd_register()

[Andrey Ryabinin]

From: Andrea Arcangeli <aarcange at redhat.com>

If the registration is repeated without VM_UFFD_MISSING or VM_UFFD_WP they
need to be cleared.  Currently setting UFFDIO_REGISTER_MODE_WP returns
-EINVAL, so this patch is a noop until the UFFDIO_REGISTER_MODE_WP support
is applied.

Link: http://lkml.kernel.org/r/20191004232834.GP13922@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange at redhat.com>
Reported-by: Wei Yang <richardw.yang at linux.intel.com>
Reviewed-by: Wei Yang <richardw.yang at linux.intel.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

https://jira.sw.ru/browse/PSBM-102938
(cherry picked from commit 9d4678eb170c4c632174d1fec8ecee31c2f314f9)
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 fs/userfaultfd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index d126b4ae57ee..2dcade9daa73 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1451,7 +1451,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 			start = vma->vm_start;
 		vma_end = min(end, vma->vm_end);
 
-		new_flags = (vma->vm_flags & ~vm_flags) | vm_flags;
+		new_flags = (vma->vm_flags &
+			     ~(VM_UFFD_MISSING|VM_UFFD_WP)) | vm_flags;
 		prev = vma_merge(mm, prev, start, vma_end, new_flags,
 				 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
 				 vma_policy(vma),
-- 
2.25.3