Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:53992 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729341AbeLNWRT (ORCPT ); Fri, 14 Dec 2018 17:17:19 -0500 Date: Fri, 14 Dec 2018 14:17:17 -0800 From: akpm@linux-foundation.org To: stable@vger.kernel.org, rppt@linux.ibm.com, peterx@redhat.com, hughd@google.com, aarcange@redhat.com, akpm@linux-foundation.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 09/11] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered Message-ID: <20181214221717.GhSVi%akpm@linux-foundation.org> Sender: stable-owner@vger.kernel.org List-ID: From: Andrea Arcangeli 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/20181206212028.18726-2-aarcange@redhat.com Cc: Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas") Signed-off-by: Andrea Arcangeli Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com Acked-by: Mike Rapoport Acked-by: Hugh Dickins Acked-by: Peter Xu Signed-off-by: Andrew Morton --- fs/userfaultfd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/userfaultfd.c~userfaultfd-check-vm_maywrite-was-set-after-verifying-the-uffd-is-registered +++ a/fs/userfaultfd.c @@ -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); _