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

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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]
Cc: <[email protected]>
Fixes: 29ec90660d ("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]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Andrea Arcangeli 2018-12-14 14:17:17 -08:00 • committed by Linus Torvalds
commit 01e881f5a1
1 changed files with 2 additions and 1 deletions
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3
fs/userfaultfd.c
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@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
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 userfaultfd_ctx *ctx,
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);