Adding qemu-stable; this fix needs to be backported to 2.5.x stable series (in the file ./nbd.c at the time), if we want to be able to allow a 2.7 client to connect to a 2.5 server.
On 04/06/2016 04:48 PM, Eric Blake wrote:
> nbd-server.c currently fails to handle unsupported options properly.
> If during option haggling the client sends an unknown request, the
> server kills the connection instead of letting the client try to
> fall back to something older. This is precisely what advertising
> NBD_FLAG_FIXED_NEWSTYLE was supposed to fix.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
> ---
>
> Turns out our server has a very similar bug to the client.
> If desired, I can spin a v3 that moves the hunk in nbd/client.c
> to the previous patch.
>
> nbd/client.c | 2 ++
> nbd/server.c | 5 ++++-
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index 67116b9..fc382c5 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -109,6 +109,8 @@ static int nbd_handle_reply_err(QIOChannel *ioc, uint32_t
> opt, uint32_t type,
>
> switch (type) {
> case NBD_REP_ERR_UNSUP:
> + TRACE("server doesn't understand request %d, attempting fallback",
> + opt);
> result = 0;
> goto cleanup;
>
> diff --git a/nbd/server.c b/nbd/server.c
> index b95571b..7843584 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -482,9 +482,12 @@ static int nbd_negotiate_options(NBDClient *client)
> return -EINVAL;
> default:
> TRACE("Unsupported option 0x%x", clientflags);
> + if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
> + return -EIO;
> + }
> nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_UNSUP,
> clientflags);
> - return -EINVAL;
> + break;
> }
> } else {
> /*
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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