Commit 01e881f5 authored Dec 14, 2018 by Andrea Arcangeli Committed by Linus Torvalds Dec 14, 2018

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/20181206212028.18726-2-aarcange@redhat.com


Cc: <stable@vger.kernel.org>
Fixes: 29ec9066 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by:  <syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 61c6de66

fs/userfaultfd.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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);

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