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userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered

PATCH New [email protected] 1 participant 1 message Dec 14, 2018

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PATCH 9/11 userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered

From: Andrea Arcangeli <[email protected]>
Subject: userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered

Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd could trigger an harmless false positive WARN_ON. Check the vma is already registered before checking VM_MAYWRITE to shut off the false positive warning.

Link http://lkml.kernel.org/r/[email protected] open here
Cc <[email protected]>
Fixes 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
Signed-off-by Andrea Arcangeli <[email protected]>
Reported-by [email protected]
Acked-by Mike Rapoport <[email protected]>
Acked-by Hugh Dickins <[email protected]>
Acked-by Peter Xu <[email protected]>
Signed-off-by Andrew Morton <[email protected]>

---

 fs/userfaultfd.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
fs/userfaultfd.c renamed from fs/userfaultfd.c~userfaultfd-check-vm_maywrite-was-set-after-verifying-the-uffd-is-registered +2 -1
@@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct
 		cond_resched();
 
 		BUG_ON(!vma_can_userfault(vma));
-		WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
 
 		/*
 		 * Nothing to do: this vma is already registered into this

@@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct
 		if (!vma->vm_userfaultfd_ctx.ctx)
 			goto skip;
 
+		WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
+
 		if (vma->vm_start > start)
 			start = vma->vm_start;
 		vma_end = min(end, vma->vm_end);

_