[PATCH 4.9 076/105] net: rtnetlink: fix info leak in RTM_GETSTATS call

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Aleksandrov <niko...@cumulusnetworks.com>


[ Upstream commit ce024f42c2e28b6bce4ecc1e891b42f57f753892 ]

When RTM_GETSTATS was added the fields of its header struct were not all
initialized when returning the result thus leaking 4 bytes of information
to user-space per rtnl_fill_statsinfo call, so initialize them now. Thanks
to Alexander Potapenko for the detailed report and bisection.

Reported-by: Alexander Potapenko <gli...@google.com>
Fixes: 10c9ead9f3c6 ("rtnetlink: add new RTM_GETSTATS message to dump link 
stats")
Signed-off-by: Nikolay Aleksandrov <niko...@cumulusnetworks.com>
Acked-by: Roopa Prabhu <ro...@cumulusnetworks.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/core/rtnetlink.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3758,6 +3758,9 @@ static int rtnl_fill_statsinfo(struct sk
                return -EMSGSIZE;
 
        ifsm = nlmsg_data(nlh);
+       ifsm->family = PF_UNSPEC;
+       ifsm->pad1 = 0;
+       ifsm->pad2 = 0;
        ifsm->ifindex = dev->ifindex;
        ifsm->filter_mask = filter_mask;