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Re: [Qemu-devel] [PATCH 3/3] nbd: Reject unknown request flags
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] nbd: Reject unknown request flags |
Date: |
Fri, 1 Apr 2016 12:47:11 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 |
On 31/03/2016 23:20, Eric Blake wrote:
> The NBD protocol says that clients should not send a command flag
> that has not been negotiated (whether by the client requesting an
> option during a handshake, or because we advertise support for the
> flag in response to NBD_OPT_EXPORT_NAME), and that servers should
> reject invalid flags with EINVAL. We were silently ignoring the
> flags instead. The client can't rely on our behavior, since it is
> their fault for passing the bad flag in the first place, but it's
> better to be robust up front than to possibly behave differently
> than the client was expecting with the attempted flag.
>
> Signed-off-by: Eric Blake <address@hidden>
> ---
> nbd/server.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/nbd/server.c b/nbd/server.c
> index a590773..31bd9c5 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -974,6 +974,10 @@ static ssize_t nbd_co_receive_request(NBDRequest *req,
> struct nbd_request *reque
> goto out;
> }
>
> + if (request->flags & ~NBD_CMD_FLAG_FUA) {
> + LOG("unsupported flags (got 0x%x)", request->flags);
> + return -EINVAL;
> + }
> if ((request->from + request->len) < request->from) {
> LOG("integer overflow detected! "
> "you're probably being attacked");
>
Queued for 2.6.
Paolo
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