From: Hugh Dickins <hughd@google.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Hugh Dickins <hughd@google.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Jann Horn <jannh@google.com>, Peter Xu <peterx@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
Date: Thu, 6 Dec 2018 14:07:51 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.11.1812061406300.1616@eggly.anvils> (raw)
In-Reply-To: <20181206212028.18726-2-aarcange@redhat.com>
On Thu, 6 Dec 2018, Andrea Arcangeli wrote:
> 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.
>
> Cc: <stable@vger.kernel.org>
> Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
> Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
> ---
> fs/userfaultfd.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cd58939dc977..7a85e609fc27 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -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);
>
next prev parent reply other threads:[~2018-12-06 22:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-06 21:20 [PATCH 0/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered Andrea Arcangeli
2018-12-06 21:20 ` [PATCH 1/1] " Andrea Arcangeli
2018-12-06 21:32 ` Mike Rapoport
2018-12-06 22:07 ` Hugh Dickins [this message]
2018-12-07 3:43 ` Peter Xu
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