xfrm: rate limit SA mapping change message to user space

Kernel generates mapping change message, XFRM_MSG_MAPPING,
when a source port chage is detected on a input state with UDP
encapsulation set.  Kernel generates a message for each IPsec packet
with new source port.  For a high speed flow per packet mapping change
message can be excessive, and can overload the user space listener.

Introduce rate limiting for XFRM_MSG_MAPPING message to the user space.

The rate limiting is configurable via netlink, when adding a new SA or
updating it. Use the new attribute XFRMA_MTIMER_THRESH in seconds.

v1->v2 change:
	update xfrm_sa_len()

v2->v3 changes:
	use u32 insted unsigned long to reduce size of struct xfrm_state
	fix xfrm_ompat size Reported-by: kernel test robot <lkp@intel.com>
	accept XFRM_MSG_MAPPING only when XFRMA_ENCAP is present

Co-developed-by: Thomas Egerer <thomas.egerer@secunet.com>
Signed-off-by: Thomas Egerer <thomas.egerer@secunet.com>
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 7c36cc1f3d79..130240680655 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -282,6 +282,10 @@ static int verify_newsa_info(struct xfrm_usersa_info *p,
 
 	err = 0;
 
+	if (attrs[XFRMA_MTIMER_THRESH])
+		if (!attrs[XFRMA_ENCAP])
+			err = -EINVAL;
+
 out:
 	return err;
 }
@@ -521,6 +525,7 @@ static void xfrm_update_ae_params(struct xfrm_state *x, struct nlattr **attrs,
 	struct nlattr *lt = attrs[XFRMA_LTIME_VAL];
 	struct nlattr *et = attrs[XFRMA_ETIMER_THRESH];
 	struct nlattr *rt = attrs[XFRMA_REPLAY_THRESH];
+	struct nlattr *mt = attrs[XFRMA_MTIMER_THRESH];
 
 	if (re) {
 		struct xfrm_replay_state_esn *replay_esn;
@@ -552,6 +557,9 @@ static void xfrm_update_ae_params(struct xfrm_state *x, struct nlattr **attrs,
 
 	if (rt)
 		x->replay_maxdiff = nla_get_u32(rt);
+
+	if (mt)
+		x->mapping_maxage = nla_get_u32(mt);
 }
 
 static void xfrm_smark_init(struct nlattr **attrs, struct xfrm_mark *m)
@@ -1024,8 +1032,13 @@ static int copy_to_user_state_extra(struct xfrm_state *x,
 		if (ret)
 			goto out;
 	}
-	if (x->security)
+	if (x->security) {
 		ret = copy_sec_ctx(x->security, skb);
+		if (ret)
+			goto out;
+	}
+	if (x->mapping_maxage)
+		ret = nla_put_u32(skb, XFRMA_MTIMER_THRESH, x->mapping_maxage);
 out:
 	return ret;
 }
@@ -3069,6 +3082,9 @@ static inline unsigned int xfrm_sa_len(struct xfrm_state *x)
 	/* Must count x->lastused as it may become non-zero behind our back. */
 	l += nla_total_size_64bit(sizeof(u64));
 
+	if (x->mapping_maxage)
+		l += nla_total_size(sizeof(x->mapping_maxage));
+
 	return l;
 }