netlink: check buffer length fits into u_int

We may increase it to size_t later, KPI allows that already, but
doesn't seem to be needed today.

Reviewed by:		melifaro
Differential Revision:	https://reviews.freebsd.org/D47550

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/netlink/netlink_io.c b/sys/netlink/netlink_io.c
index bc8d2f9fcc3f..d2022a6a2b0d 100644
--- a/sys/netlink/netlink_io.c
+++ b/sys/netlink/netlink_io.c
@@ -58,6 +58,9 @@ nl_buf_alloc(size_t len, int mflag)
 {
 	struct nl_buf *nb;
 
+	KASSERT(len > 0 && len <= UINT_MAX, ("%s: invalid length %zu",
+	    __func__, len));
+
 	nb = malloc(sizeof(struct nl_buf) + len, M_NETLINK, mflag);
 	if (__predict_true(nb != NULL)) {
 		nb->buflen = len;