net: fib_rules: annotate data-races around rule->[io]ifindex

BugLink: https://bugs.launchpad.net/bugs/2104873

[ Upstream commit cb827db ]

rule->iifindex and rule->oifindex can be read without holding RTNL.

Add READ_ONCE()/WRITE_ONCE() annotations where needed.

Fixes: 32affa5 ("fib: rules: no longer hold RTNL in fib_nl_dumprule()")
Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Reviewed-by: Ido Schimmel <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Noah Wager <[email protected]>

Author: edumazet

net/core/fib_rules.c

@@ -36,8 +36,8 @@ static const struct fib_kuid_range fib_kuid_range_unset = {
 
 bool fib_rule_matchall(const struct fib_rule *rule)
 {
-	if (rule->iifindex || rule->oifindex || rule->mark || rule->tun_id ||
-	    rule->flags)
+	if (READ_ONCE(rule->iifindex) || READ_ONCE(rule->oifindex) ||
+	    rule->mark || rule->tun_id || rule->flags)
 		return false;
 	if (rule->suppress_ifgroup != -1 || rule->suppress_prefixlen != -1)
 		return false;
@@ -259,12 +259,14 @@ static int fib_rule_match(struct fib_rule *rule, struct fib_rules_ops *ops,
 			  struct flowi *fl, int flags,
 			  struct fib_lookup_arg *arg)
 {
-	int ret = 0;
+	int iifindex, oifindex, ret = 0;
 
-	if (rule->iifindex && (rule->iifindex != fl->flowi_iif))
+	iifindex = READ_ONCE(rule->iifindex);
+	if (iifindex && (iifindex != fl->flowi_iif))
 		goto out;
 
-	if (rule->oifindex && (rule->oifindex != fl->flowi_oif))
+	oifindex = READ_ONCE(rule->oifindex);
+	if (oifindex && (oifindex != fl->flowi_oif))
 		goto out;
 
 	if ((rule->mark ^ fl->flowi_mark) & rule->mark_mask)
@@ -1036,14 +1038,14 @@ static int fib_nl_fill_rule(struct sk_buff *skb, struct fib_rule *rule,
 	if (rule->iifname[0]) {
 		if (nla_put_string(skb, FRA_IIFNAME, rule->iifname))
 			goto nla_put_failure;
-		if (rule->iifindex == -1)
+		if (READ_ONCE(rule->iifindex) == -1)
 			frh->flags |= FIB_RULE_IIF_DETACHED;
 	}
 
 	if (rule->oifname[0]) {
 		if (nla_put_string(skb, FRA_OIFNAME, rule->oifname))
 			goto nla_put_failure;
-		if (rule->oifindex == -1)
+		if (READ_ONCE(rule->oifindex) == -1)
 			frh->flags |= FIB_RULE_OIF_DETACHED;
 	}
 
@@ -1216,10 +1218,10 @@ static void attach_rules(struct list_head *rules, struct net_device *dev)
 	list_for_each_entry(rule, rules, list) {
 		if (rule->iifindex == -1 &&
 		    strcmp(dev->name, rule->iifname) == 0)
-			rule->iifindex = dev->ifindex;
+			WRITE_ONCE(rule->iifindex, dev->ifindex);
 		if (rule->oifindex == -1 &&
 		    strcmp(dev->name, rule->oifname) == 0)
-			rule->oifindex = dev->ifindex;
+			WRITE_ONCE(rule->oifindex, dev->ifindex);
 	}
 }
 
@@ -1229,9 +1231,9 @@ static void detach_rules(struct list_head *rules, struct net_device *dev)
 
 	list_for_each_entry(rule, rules, list) {
 		if (rule->iifindex == dev->ifindex)
-			rule->iifindex = -1;
+			WRITE_ONCE(rule->iifindex, -1);
 		if (rule->oifindex == dev->ifindex)
-			rule->oifindex = -1;
+			WRITE_ONCE(rule->oifindex, -1);
 	}
 }