linux-kernel - [PATCH AUTOSEL 6.1 24/29] net: ipv6: rpl_iptunnel: block BH in rpl_output() and rpl

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Date: Tue, 18 Jun 2024 08:39:50 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>,
	Alexander Aring <aahringo@...hat.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	davem@...emloft.net,
	dsahern@...nel.org,
	netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.1 24/29] net: ipv6: rpl_iptunnel: block BH in rpl_output() and rpl_input()

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit db0090c6eb12c31246438b7fe2a8f1b833e7a653 ]

As explained in commit 1378817486d6 ("tipc: block BH
before using dst_cache"), net/core/dst_cache.c
helpers need to be called with BH disabled.

Disabling preemption in rpl_output() is not good enough,
because rpl_output() is called from process context,
lwtunnel_output() only uses rcu_read_lock().

We might be interrupted by a softirq, re-enter rpl_output()
and corrupt dst_cache data structures.

Fix the race by using local_bh_disable() instead of
preempt_disable().

Apply a similar change in rpl_input().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Alexander Aring <aahringo@...hat.com>
Acked-by: Paolo Abeni <pabeni@...hat.com>
Link: https://lore.kernel.org/r/20240531132636.2637995-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv6/rpl_iptunnel.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/rpl_iptunnel.c b/net/ipv6/rpl_iptunnel.c
index ff691d9f4a04f..26adbe7f8a2f0 100644
--- a/net/ipv6/rpl_iptunnel.c
+++ b/net/ipv6/rpl_iptunnel.c
@@ -212,9 +212,9 @@ static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 	if (unlikely(err))
 		goto drop;
 
-	preempt_disable();
+	local_bh_disable();
 	dst = dst_cache_get(&rlwt->cache);
-	preempt_enable();
+	local_bh_enable();
 
 	if (unlikely(!dst)) {
 		struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -234,9 +234,9 @@ static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 			goto drop;
 		}
 
-		preempt_disable();
+		local_bh_disable();
 		dst_cache_set_ip6(&rlwt->cache, dst, &fl6.saddr);
-		preempt_enable();
+		local_bh_enable();
 	}
 
 	skb_dst_drop(skb);
@@ -268,9 +268,8 @@ static int rpl_input(struct sk_buff *skb)
 		return err;
 	}
 
-	preempt_disable();
+	local_bh_disable();
 	dst = dst_cache_get(&rlwt->cache);
-	preempt_enable();
 
 	skb_dst_drop(skb);
 
@@ -278,14 +277,13 @@ static int rpl_input(struct sk_buff *skb)
 		ip6_route_input(skb);
 		dst = skb_dst(skb);
 		if (!dst->error) {
-			preempt_disable();
 			dst_cache_set_ip6(&rlwt->cache, dst,
 					  &ipv6_hdr(skb)->saddr);
-			preempt_enable();
 		}
 	} else {
 		skb_dst_set(skb, dst);
 	}
+	local_bh_enable();
 
 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 	if (unlikely(err))
-- 
2.43.0