Re: [patch v8 3/7] nbd: check sock index in nbd_read_stat()

[yukuai (C)]

On 2021/09/22 17:22, Ming Lei wrote:
> On Sun, Sep 19, 2021 at 06:34:28PM +0800, yukuai (C) wrote:
> > On 2021/09/16 17:33, Yu Kuai wrote:
> > > The sock that clent send request in nbd_send_cmd() and receive reply
> > > in nbd_read_stat() should be the same.
> > >
> > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > > ---
> > >    drivers/block/nbd.c | 4 ++++
> > >    1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> > > index 614c6ab2b8fe..c724a5bd7fa4 100644
> > > --- a/drivers/block/nbd.c
> > > +++ b/drivers/block/nbd.c
> > > @@ -746,6 +746,10 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
> > >    		ret = -ENOENT;
> > >    		goto out;
> > >    	}
> > > +	if (cmd->index != index) {
> > > +		dev_err(disk_to_dev(nbd->disk), "Unexpected reply %d from different sock %d (expected %d)",
> > > +			tag, index, cmd->index);
> > > +	}
> > >    	if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) {
> > >    		dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n",
> > >    			req, cmd->cmd_cookie, nbd_handle_to_cookie(handle));
> >
> > Hi, Ming
> >
> > Any suggestions about this patch?
>
> I think this one relies on nbd protocol between server and client, and
> does the protocol require both request and reply xmitted via same
> socket?

I searched nbd-server source code, and found that socket_read() and
send_reply->socket_write() are always come in pares and using the same
socket.

BTW, if server reply a read request from a unexpected sock, then
nbd_read_stat() might stuck in receiving the read data. And for worse,
nbd_read_stat() can mistake the normal reply message for the read data
afterwards and corrupt client.

Thanks,
Kuai