Subject: [PATCH net-next 14/20] net/neighbor: Update neigh_dump_info for strict data checking

From: David Ahern <[email-masked]>
Date: Thu, 4 Oct 2018 14:33:49 -0700

From: David Ahern <[email-masked]>

Update neigh_dump_info for strict data checking. If the flag is set,
the dump request is expected to have an ndmsg struct as the header
potentially followed by one or more attributes. Any data passed in the
header or as an attribute is taken as a request to influence the data
returned. Only values supported by the dump handler are allowed to be
non-0 or set in the request. At the moment only the NDA_IFINDEX and
NDA_MASTER attributes are supported.

Existing code does not fail the dump if nlmsg_parse fails. That behavior
is kept for non-strict checking.

Signed-off-by: David Ahern <[email-masked]>
---
 net/core/neighbour.c | 59 ++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 11 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index b06f794bf91e..3130d010b7ad 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2428,13 +2428,14 @@ static int pneigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 
 static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	struct netlink_ext_ack *extack = cb->extack;
 	const struct nlmsghdr *nlh = cb->nlh;
 	struct neigh_dump_filter filter = {};
 	struct nlattr *tb[NDA_MAX + 1];
 	struct neigh_table *tbl;
 	int t, family, s_t;
 	int proxy = 0;
-	int err;
+	int err, i;
 
 	family = ((struct rtgenmsg *)nlmsg_data(nlh))->rtgen_family;
 
@@ -2445,20 +2446,56 @@ static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 	    ((struct ndmsg *)nlmsg_data(nlh))->ndm_flags == NTF_PROXY)
 		proxy = 1;
 
-	err = nlmsg_parse(nlh, sizeof(struct ndmsg), tb, NDA_MAX, NULL,
-			  cb->extack);
-	if (!err) {
-		if (tb[NDA_IFINDEX]) {
-			if (nla_len(tb[NDA_IFINDEX]) != sizeof(u32))
-				return -EINVAL;
-			filter.dev_idx = nla_get_u32(tb[NDA_IFINDEX]);
+	if (cb->strict_check) {
+		struct ndmsg *ndm;
+
+		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ndm))) {
+			NL_SET_ERR_MSG(extack, "Invalid header");
+			return -EINVAL;
+		}
+
+		ndm = nlmsg_data(nlh);
+		if (ndm->ndm_pad1  || ndm->ndm_pad2  || ndm->ndm_ifindex ||
+		    ndm->ndm_state || ndm->ndm_flags || ndm->ndm_type) {
+			NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
+			return -EINVAL;
 		}
-		if (tb[NDA_MASTER]) {
-			if (nla_len(tb[NDA_MASTER]) != sizeof(u32))
+	}
+
+	err = nlmsg_parse(nlh, sizeof(struct ndmsg), tb, NDA_MAX, NULL, extack);
+	if (err < 0) {
+		if (cb->strict_check)
+			return -EINVAL;
+		goto walk_entries;
+	}
+
+	for (i = 0; i <= NDA_MAX; ++i) {
+		if (!tb[i])
+			continue;
+		switch (i) {
+		case NDA_IFINDEX:
+			if (nla_len(tb[i]) != sizeof(u32)) {
+				NL_SET_ERR_MSG(extack, "Invalid IFINDEX attribute");
 				return -EINVAL;
-			filter.master_idx = nla_get_u32(tb[NDA_MASTER]);
+			}
+			filter.dev_idx = nla_get_u32(tb[i]);
+			break;
+		case NDA_MASTER:
+			if (nla_len(tb[i]) != sizeof(u32)) {
+				NL_SET_ERR_MSG(extack, "Invalid MASTER attribute");
+				return -EINVAL;
+			}
+			filter.master_idx = nla_get_u32(tb[i]);
+			break;
+		default:
+			if (cb->strict_check) {
+				NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
+				return -EINVAL;
+			}
 		}
 	}
+
+walk_entries:
 	s_t = cb->args[0];
 
 	for (t = 0; t < NEIGH_NR_TABLES; t++) {
-- 
2.11.0