[PATCH] fib:fix BUG_ON in fib_nl_newrule when add new fib rule

From: Gao feng <redacted>

add new fib rule can cause BUG_ON
the reproduce shell is

#ip rule add pref 38
#ip rule add pref 38
#ip rule add to 192.168.3.0/24 goto 38
#ip rule del pref 38
#ip rule add to 192.168.3.0/24 goto 38
#ip rule add pref 38

then the BUG_ON will happen
add a var unresolved in struct fib_rule
and use it to identify whether this rule is unresolved

Signed-off-by: Gao feng <redacted>
---
 include/net/fib_rules.h |    1 +
 net/core/fib_rules.c    |    5 ++++-
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index 075f1e3..e4bae01 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h

@@ -19,6 +19,7 @@ struct fib_rule {
 	u32			flags;
 	u32			table;
 	u8			action;
+	u8			unresolved;
 	u32			target;
 	struct fib_rule __rcu	*ctarget;
 	char			iifname[IFNAMSIZ];

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index e7ab0c0..aa20560 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c

@@ -384,9 +384,11 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 		 */
 		list_for_each_entry(r, &ops->rules_list, list) {
 			if (r->action == FR_ACT_GOTO &&
-			    r->target == rule->pref) {
+			    r->target == rule->pref &&
+			    r->unresolved) {
 				BUG_ON(rtnl_dereference(r->ctarget) != NULL);
 				rcu_assign_pointer(r->ctarget, rule);
+				r->unresolved = 0;
 				if (--ops->unresolved_rules == 0)
 					break;
 			}

@@ -488,6 +490,7 @@ static int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 			list_for_each_entry(tmp, &ops->rules_list, list) {
 				if (rtnl_dereference(tmp->ctarget) == rule) {
 					rcu_assign_pointer(tmp->ctarget, NULL);
+					tmp->unresolved = 1;
 					ops->unresolved_rules++;
 				}
 			}

-- 
1.7.6

Le dimanche 11 septembre 2011 à 01:19 +0800, Wanlong Gao a écrit :

Hmm, good catch, but you add 'unresolved' field but dont init it
correctly to 1 in all cases.

Following will break :

ip rule add pref 100
ip rule add to 192.168.3.0/24 goto 200
ip rule add pref 200

Normally, we should have 

unresolved = (ctarget == NULL);

What about following patch instead ?

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index e7ab0c0..3231b46 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c

@@ -384,8 +384,8 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 		 */
 		list_for_each_entry(r, &ops->rules_list, list) {
 			if (r->action == FR_ACT_GOTO &&
-			    r->target == rule->pref) {
-				BUG_ON(rtnl_dereference(r->ctarget) != NULL);
+			    r->target == rule->pref &&
+			    rtnl_dereference(r->ctarget) == NULL) {
 				rcu_assign_pointer(r->ctarget, rule);
 				if (--ops->unresolved_rules == 0)
 					break;

From: Gao feng <redacted>

add new fib rule can cause BUG_ON happen
the reproduce shell is
ip rule add pref 38
ip rule add pref 38
ip rule add to 192.168.3.0/24 goto 38
ip rule del pref 38
ip rule add to 192.168.3.0/24 goto 38
ip rule add pref 38

then the BUG_ON will happen
del BUG_ON and use (ctarget == NULL) identify whether this rule is unresolved

Signed-off-by: Gao feng <redacted>
Signed-off-by: Eric Dumazet <redacted>
---
 net/core/fib_rules.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index e7ab0c0..3231b46 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c

@@ -384,8 +384,8 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 		 */
 		list_for_each_entry(r, &ops->rules_list, list) {
 			if (r->action == FR_ACT_GOTO &&
-			    r->target == rule->pref) {
-				BUG_ON(rtnl_dereference(r->ctarget) != NULL);
+			    r->target == rule->pref &&
+			    rtnl_dereference(r->ctarget) == NULL) {
 				rcu_assign_pointer(r->ctarget, rule);
 				if (--ops->unresolved_rules == 0)
 					break;

-- 
1.7.6

From: Wanlong Gao <redacted>
Date: Mon, 12 Sep 2011 09:36:05 +0800

From: Gao feng <redacted>

add new fib rule can cause BUG_ON happen
the reproduce shell is
ip rule add pref 38
ip rule add pref 38
ip rule add to 192.168.3.0/24 goto 38
ip rule del pref 38
ip rule add to 192.168.3.0/24 goto 38
ip rule add pref 38

then the BUG_ON will happen
del BUG_ON and use (ctarget == NULL) identify whether this rule is unresolved

Signed-off-by: Gao feng <redacted>
Signed-off-by: Eric Dumazet <redacted>

Applied, thanks a lot.