[PATCH net-next 17/20] net/fib_rules: Update fib_nl_dumprule for strict data checking

[David Ahern]

From: David Ahern <dsah...@gmail.com>

Update fib_nl_dumprule for strict data checking. If the flag is set,
the dump request is expected to have fib_rule_hdr struct as the header.
All elements of the struct are expected to be 0 and no attributes can
be appended.

Signed-off-by: David Ahern <dsah...@gmail.com>
---
 net/core/fib_rules.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 0ff3953f64aa..e3cf50728d0a 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -1063,13 +1063,47 @@ static int dump_rules(struct sk_buff *skb, struct 
netlink_callback *cb,
        return err;
 }
 
+static int fib_valid_dumprule(const struct nlmsghdr *nlh,
+                             struct netlink_ext_ack *extack)
+{
+       struct fib_rule_hdr *frh;
+
+       if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh))) {
+               NL_SET_ERR_MSG(extack, "Invalid header");
+               return -EINVAL;
+       }
+
+       frh = nlmsg_data(nlh);
+       if (frh->dst_len || frh->src_len || frh->tos || frh->table ||
+           frh->res1 || frh->res2 || frh->action || frh->flags) {
+               NL_SET_ERR_MSG(extack,
+                              "Invalid values in header for dump request");
+               return -EINVAL;
+       }
+
+       if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*frh))) {
+               NL_SET_ERR_MSG(extack, "Invalid data after header");
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
 static int fib_nl_dumprule(struct sk_buff *skb, struct netlink_callback *cb)
 {
+       const struct nlmsghdr *nlh = cb->nlh;
        struct net *net = sock_net(skb->sk);
        struct fib_rules_ops *ops;
        int idx = 0, family;
 
-       family = rtnl_msg_family(cb->nlh);
+       if (cb->strict_check) {
+               int err = fib_valid_dumprule(nlh, cb->extack);
+
+               if (err)
+                       return err;
+       }
+
+       family = rtnl_msg_family(nlh);
        if (family != AF_UNSPEC) {
                /* Protocol specific dump request */
                ops = lookup_rules_ops(net, family);
-- 
2.11.0