On Wed, May 16, 2018 at 03:32:59PM +0800, Jason Wang wrote:
>
>
> On 2018年05月16日 15:12, Andrei Vagin wrote:
> > Hi Jason,
> >
> > I think the problem is in "tun: hold a tun socket during ptr_ring_cleanup".
> >
> > Pls take a look at the attached patch.
>
> Yes.
>
> It looks to me it's not necessary to take extra refcnt during release, we
> can just do the cleanup at __tun_detach().
>
> Could you help to test the attached patch?
I've run my test on the kernel with this patch. It fixes the problem.
The patch looks correct for me.
Acked-by: Andrei Vagin <ava...@virtuozzo.com>
>
> Thanks
>
> From 4b5ad75208e379dcb32abb9ac4790a0446f8558b Mon Sep 17 00:00:00 2001
> From: Jason Wang <jasow...@redhat.com>
> Date: Wed, 16 May 2018 15:26:52 +0800
> Subject: [PATCH] tuntap: fix use after free during release
>
> After commit b196d88aba8a ("tun: fix use after free for ptr_ring") we
> need clean up tx ring during release(). But unfortunately, it tries to
> do the cleanup after socket were destroyed which will lead another
> use-after-free. Fix this by doing the cleanup before dropping the last
> reference of the socket in __tun_detach().
>
> Reported-by: Andrei Vagin <ava...@virtuozzo.com>
> Fixes: b196d88aba8a ("tun: fix use after free for ptr_ring")
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> drivers/net/tun.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 9fbbb32..d45ac37 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -729,6 +729,7 @@ static void __tun_detach(struct tun_file *tfile, bool
> clean)
> }
> if (tun)
> xdp_rxq_info_unreg(&tfile->xdp_rxq);
> + ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
> sock_put(&tfile->sk);
> }
> }
> @@ -3245,7 +3246,6 @@ static int tun_chr_close(struct inode *inode, struct
> file *file)
> struct tun_file *tfile = file->private_data;
>
> tun_detach(tfile, true);
> - ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
>
> return 0;
> }
> --
> 2.7.4
>
