linux-kernel - RE: [PATCH] tools/hv/hv_kvp_daemon.c: Netlink source address validation allows DoS

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Date:	Tue, 6 Nov 2012 19:58:40 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Tomas Hozza <thozza@...hat.com>
CC:	Olaf Hering <olaf@...fle.de>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH] tools/hv/hv_kvp_daemon.c: Netlink source address
 validation allows DoS



> -----Original Message-----
> From: Tomas Hozza [mailto:thozza@...hat.com]
> Sent: Tuesday, November 06, 2012 2:55 PM
> To: KY Srinivasan
> Cc: Olaf Hering; gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> devel@...uxdriverproject.org; apw@...onical.com; jasowang@...hat.com
> Subject: Re: [PATCH] tools/hv/hv_kvp_daemon.c: Netlink source address
> validation allows DoS
> 
> From 6199072f8131056efce208f04e6985d1f9968d8e Mon Sep 17 00:00:00 2001
> From: Tomas Hozza <thozza@...hat.com>
> Date: Mon, 5 Nov 2012 10:08:16 +0100
> Subject: [PATCH] Netlink source address validation allows DoS
> 
> The source code without this patch caused hypervkvpd to exit when it processed
> a spoofed Netlink packet which has been sent from an untrusted local user.
> Netlink messages with a non-zero nl_pid source address should just be ignored.

Thomas,

You need a Signed-off-by line. Please refer to the documentation on how to submit a patch.

Regards,

K. Y
> ---
>  tools/hv/hv_kvp_daemon.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
> index 3ea3af2..7d74497 100755
> --- a/tools/hv/hv_kvp_daemon.c
> +++ b/tools/hv/hv_kvp_daemon.c
> @@ -1478,13 +1478,19 @@ int main(void)
>  		len = recvfrom(fd, kvp_recv_buffer, sizeof(kvp_recv_buffer), 0,
>  				addr_p, &addr_l);
> 
> -		if (len < 0 || addr.nl_pid) {
> +		if (len < 0) {
>  			syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
>  					addr.nl_pid, errno, strerror(errno));
>  			close(fd);
>  			return -1;
>  		}
> 
> +		if (addr.nl_pid) {
> +			syslog(LOG_WARNING, "Received packet from untrusted
> pid:%u",
> +					addr.nl_pid);
> +			continue;
> +		}
> +
>  		incoming_msg = (struct nlmsghdr *)kvp_recv_buffer;
>  		incoming_cn_msg = (struct cn_msg
> *)NLMSG_DATA(incoming_msg);
>  		hv_msg = (struct hv_kvp_msg *)incoming_cn_msg->data;
> --
> 1.7.11.7
> 
> ----- Original Message -----
> >
> >
> > > -----Original Message-----
> > > From: Tomas Hozza [mailto:thozza@...hat.com]
> > > Sent: Tuesday, November 06, 2012 10:21 AM
> > > To: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> > > devel@...uxdriverproject.org; apw@...onical.com;
> > > jasowang@...hat.com
> > > Cc: Olaf Hering; KY Srinivasan
> > > Subject: [PATCH] tools/hv/hv_kvp_daemon.c: Netlink source address
> > > validation
> > > allows DoS
> > >
> > > Hi.
> > >
> > > After discussion with KY Srinivasan and Olaf Hering I'm sending you
> > > a patch for the HyperV KVP daemon distributed in linux kernel
> > > "tools/hv/hv_kvp_daemon.c".
> > >
> > > There is an issue in the current daemon source causing hyperv kvp
> > > daemon
> > > to exit when it processes a spoofed Netlink packet which has been
> > > sent
> > > from an untrusted local user.
> > >
> > > This patch is fixing this, so now the Netlink messages with a
> > > non-zero
> > > nl_pid source address are just ignored.
> >
> > You don't want to send the patch as an attachment.  Please send the
> > patch
> > as part of the mail.
> >
> > Regards,
> >
> > K. Y
> > >
> > >
> > > Regards,
> > >
> > > Tomas Hozza
> > > Associate Software Engineer
> > > BaseOS - Brno, CZ
> >
>