On Thu, Oct 17, 2019 at 04:27:34PM -0500, Mike Christie wrote:
> nbd requires socket families to support the shutdown method so the nbd
> recv workqueue can be woken up from its sock_recvmsg call. If the socket
> does not support the callout we will leave recv works running or get hangs
> later when the device or module is removed.
>
> This adds a check during socket connection/reconnection to make sure the
> socket being passed in supports the needed callout.
>
> Reported-by: syzbot+24c12fa8d218ed26011a@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: e9e006f5fcf2 ("nbd: fix max number of supported devs")
> Signed-off-by: Mike Christie <mchristi@xxxxxxxxxx>
I tested this patch to try to make sure it doesn't break typical
existing use cases of the kernel NBD client using Unix and TCP
servers. I used a Fedora 30 virtual machine, nbdkit-1.12.8-1.fc30,
and the upstream kernel + your patch for testing. I tested it using
loop-style commands similar to what I did in this talk[1] using
commands from the nbdkit manual[2].
Note I did *not* test the negative case, eg. NBD over a netlink
socket, as I have no easy way to test that.
Anyway, I can confirm that both Unix domain sockets and TCP to
localhost works fine with this patch, so:
Tested-by: Richard W.M. Jones <rjones@xxxxxxxxxx>
Rich.
[1] https://archive.fosdem.org/2019/schedule/event/nbdkit/
[2] http://libguestfs.org/nbdkit-loop.1.html
> ---
> drivers/block/nbd.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 478aa86fc1f2..7bd9e92f6bb7 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -972,6 +972,25 @@ static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
> return ret;
> }
>
> +static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd,
> + int *err)
> +{
> + struct socket *sock;
> +
> + *err = 0;
> + sock = sockfd_lookup(fd, err);
> + if (!sock)
> + return NULL;
> +
> + if (sock->ops->shutdown == sock_no_shutdown) {
> + dev_err(disk_to_dev(nbd->disk), "Unsupported socket: shutdown callout must be supported.\n");
> + *err = -EINVAL;
> + return NULL;
> + }
> +
> + return sock;
> +}
> +
> static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
> bool netlink)
> {
> @@ -981,7 +1000,7 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
> struct nbd_sock *nsock;
> int err;
>
> - sock = sockfd_lookup(arg, &err);
> + sock = nbd_get_socket(nbd, arg, &err);
> if (!sock)
> return err;
>
> @@ -1033,7 +1052,7 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
> int i;
> int err;
>
> - sock = sockfd_lookup(arg, &err);
> + sock = nbd_get_socket(nbd, arg, &err);
> if (!sock)
> return err;
>
> --
> 2.20.1
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines. Supports shell scripting,
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