RE: [PATCH] tools: hv: Netlink source address validation allows DoS

[KY Srinivasan]

> -----Original Message-----
> From: Tomas Hozza [mailto:thozza@xxxxxxxxxx]
> Sent: Thursday, November 08, 2012 4:53 AM
> To: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx;
> jasowang@xxxxxxxxxx; KY Srinivasan
> Cc: Tomas Hozza
> Subject: [PATCH] tools: hv: 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.
> Now Netlink messages with a non-zero nl_pid source address are ignored
> and a warning is printed into the syslog.
> 
> Signed-off-by: Tomas Hozza <thozza@xxxxxxxxxx>
Acked-by:  K. Y. Srinivasan <kys@xxxxxxxxxxxxx>

> ---
>  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 13c2a14..c1d9102 100755
> --- a/tools/hv/hv_kvp_daemon.c
> +++ b/tools/hv/hv_kvp_daemon.c
> @@ -1486,13 +1486,19 @@ 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
> 
> 


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