From 054948bd81bb9e4e32449cf351b62e501b8831ff Mon Sep 17 00:00:00 2001
From: "Alexander V. Chernikov" <melifaro@FreeBSD.org>
Date: Sun, 1 Aug 2021 09:46:05 +0000
Subject: [PATCH] [multipath][nhops] Fix random crashes with high route churn
 rate.

When certain multipath route begins flapping really fast, it may
 result in creating multiple identical nexthop groups. The code
 responsible for unlinking unused nexthop groups had an implicit
 assumption that there could be only one nexthop group for the
 same combination of nexthops with weights. This assumption resulted
 in always unlinking the first "identical" group, instead of the
 desired one. Such action, in turn, produced a used-but-unlinked
 nhg along with freed-and-linked nhg, ending up in random crashes.

Similarly, it is possible that multiple identical nexthops gets
 created in the case of high route churn, resulting in the same
 problem when deleting one of such nexthops.

Fix by matching the nexthop/nexhop group pointer when deleting the item.

Reported by:	avg
MFC after:	1 week
---
 sys/net/route/nhgrp.c      |  2 +-
 sys/net/route/nhop.c       |  2 +-
 sys/net/route/nhop_utils.h | 23 +++--------------------
 3 files changed, 5 insertions(+), 22 deletions(-)

diff --git a/sys/net/route/nhgrp.c b/sys/net/route/nhgrp.c
index f763cc25fd5c..982ff2a72f15 100644
--- a/sys/net/route/nhgrp.c
+++ b/sys/net/route/nhgrp.c
@@ -187,7 +187,7 @@ unlink_nhgrp(struct nh_control *ctl, struct nhgrp_priv *key)
 
 	NHOPS_WLOCK(ctl);
 
-	CHT_SLIST_REMOVE_BYOBJ(&ctl->gr_head, mpath, key, nhg_priv_ret);
+	CHT_SLIST_REMOVE(&ctl->gr_head, mpath, key, nhg_priv_ret);
 
 	if (nhg_priv_ret == NULL) {
 		DPRINTF("Unable to find nhop group!");
diff --git a/sys/net/route/nhop.c b/sys/net/route/nhop.c
index 0db47db9916e..ab5e393ae56a 100644
--- a/sys/net/route/nhop.c
+++ b/sys/net/route/nhop.c
@@ -337,7 +337,7 @@ unlink_nhop(struct nh_control *ctl, struct nhop_priv *nh_priv_del)
 	idx = 0;
 
 	NHOPS_WLOCK(ctl);
-	CHT_SLIST_REMOVE_BYOBJ(&ctl->nh_head, nhops, nh_priv_del, priv_ret);
+	CHT_SLIST_REMOVE(&ctl->nh_head, nhops, nh_priv_del, priv_ret);
 
 	if (priv_ret != NULL) {
 		idx = priv_ret->nh_idx;
diff --git a/sys/net/route/nhop_utils.h b/sys/net/route/nhop_utils.h
index a0d7cd564e72..1f56f4cb8b0b 100644
--- a/sys/net/route/nhop_utils.h
+++ b/sys/net/route/nhop_utils.h
@@ -115,31 +115,13 @@ struct _HNAME##_head {				\
 	(_head)->items_count++;						\
 } while(0)
 
-#define	CHT_SLIST_REMOVE(_head, _PX, _key, _ret) do {			\
-	typeof(*(_head)->ptr) _tmp;					\
-	uint32_t _buck = CHT_GET_BUCK(_head, _PX, _key);		\
-	_ret = CHT_FIRST(_head, _buck);					\
-	_tmp = NULL;							\
-	for ( ; _ret != NULL; _tmp = _ret, _ret = _PX##_next(_ret)) {	\
-		if (_PX##_cmp(_key, _ret))				\
-			break;						\
-	}								\
-	if (_ret != NULL) {						\
-		if (_tmp == NULL)					\
-			CHT_FIRST(_head, _buck) = _PX##_next(_ret);	\
-		else							\
-			_PX##_next(_tmp) = _PX##_next(_ret);		\
-		(_head)->items_count--;					\
-	}								\
-} while(0)
-
-#define	CHT_SLIST_REMOVE_BYOBJ(_head, _PX, _obj, _ret) do {		\
+#define	CHT_SLIST_REMOVE(_head, _PX, _obj, _ret) do {			\
 	typeof(*(_head)->ptr) _tmp;					\
 	uint32_t _buck = CHT_GET_BUCK_OBJ(_head, _PX, _obj);		\
 	_ret = CHT_FIRST(_head, _buck);					\
 	_tmp = NULL;							\
 	for ( ; _ret != NULL; _tmp = _ret, _ret = _PX##_next(_ret)) {	\
-		if (_PX##_cmp(_obj, _ret))				\
+		if (_obj == _ret)					\
 			break;						\
 	}								\
 	if (_ret != NULL) {						\
@@ -150,6 +132,7 @@ struct _HNAME##_head {				\
 		(_head)->items_count--;					\
 	}								\
 } while(0)
+#define	CHT_SLIST_REMOVE_BYOBJ	CHT_SLIST_REMOVE
 
 #define	CHT_SLIST_FOREACH(_head, _PX, _x)				\
 	for (uint32_t _i = 0; _i < (_head)->hash_size; _i++) {		\