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

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Message-ID: <20250206083051.2494877-1-edumazet@google.com>
Date: Thu,  6 Feb 2025 08:30:51 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, David Ahern <dsahern@...nel.org>, 
	Simon Horman <horms@...nel.org>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] net: fib_rules: annotate data-races around rule->[io]ifindex

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

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

Fixes: 32affa5578f0 ("fib: rules: no longer hold RTNL in fib_nl_dumprule()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/fib_rules.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index e684ba3ebb38563abefc034c16ba381635285953..94a7872ab231855dd9965efb099c09fe3728e1a2 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -37,8 +37,8 @@ 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;
@@ -261,12 +261,14 @@ 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)
@@ -1041,14 +1043,14 @@ 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;
 	}
 
@@ -1220,10 +1222,10 @@ 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);
 	}
 }
 
@@ -1233,9 +1235,9 @@ 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);
 	}
 }
 
-- 
2.48.1.362.g079036d154-goog