bugfix: the scheduler template (dn_schk) for the round robin scheduler

is followed by another structure (rr_schk) whose size must be set
in the schk_datalen field of the descriptor.
Not allocating the memory may cause other memory to be overwritten
(though dn_schk is 192 bytes and rr_schk only 12 so we may be lucky
and end up in the padding after the dn_schk).

This is a merge candidate for stable and 10.3

MFC after:	3 days

1 files changed, 2 insertions, 1 deletions

diff --git a/sys/netpfil/ipfw/dn_sched_rr.c b/sys/netpfil/ipfw/dn_sched_rr.c
index 63e525a2b7a0..16649a82e638 100644
--- a/sys/netpfil/ipfw/dn_sched_rr.c
+++ b/sys/netpfil/ipfw/dn_sched_rr.c
@@ -294,7 +294,7 @@ static struct dn_alg rr_desc = {
 	_SI( .name = ) "RR",
 	_SI( .flags = ) DN_MULTIQUEUE,
 
-	_SI( .schk_datalen = ) 0,
+	_SI( .schk_datalen = ) sizeof(struct rr_schk),
 	_SI( .si_datalen = ) sizeof(struct rr_si),
 	_SI( .q_datalen = ) sizeof(struct rr_queue) - sizeof(struct dn_queue),
 
@@ -311,5 +311,6 @@ static struct dn_alg rr_desc = {
 	_SI( .free_queue = ) rr_free_queue,
 };
 
+_Static_assert(sizeof(struct dn_schk) < 193, "a");
 
 DECLARE_DNSCHED_MODULE(dn_rr, &rr_desc);