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@redhat.com>
Acked-by:  K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
index 13c2a142331d..c1d910243d49 100644
--- 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;