netdev - [PATCH net 4/5] ila: block BH in ila

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Date: Fri, 31 May 2024 13:26:35 +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, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 4/5] ila: block BH in ila_output()

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.

ila_output() is called from lwtunnel_output()
possibly from process context, and under rcu_read_lock().

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

Fix the race by using local_bh_disable().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/ila/ila_lwt.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ila/ila_lwt.c b/net/ipv6/ila/ila_lwt.c
index 0601bad798221389fe83318fbb17f192cec880d4..ff7e734e335b06f03c4c8815163a706136e42a3e 100644
--- a/net/ipv6/ila/ila_lwt.c
+++ b/net/ipv6/ila/ila_lwt.c
@@ -58,7 +58,9 @@ static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 		return orig_dst->lwtstate->orig_output(net, sk, skb);
 	}
 
+	local_bh_disable();
 	dst = dst_cache_get(&ilwt->dst_cache);
+	local_bh_enable();
 	if (unlikely(!dst)) {
 		struct ipv6hdr *ip6h = ipv6_hdr(skb);
 		struct flowi6 fl6;
@@ -86,8 +88,11 @@ static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 			goto drop;
 		}
 
-		if (ilwt->connected)
+		if (ilwt->connected) {
+			local_bh_disable();
 			dst_cache_set_ip6(&ilwt->dst_cache, dst, &fl6.saddr);
+			local_bh_enable();
+		}
 	}
 
 	skb_dst_set(skb, dst);
-- 
2.45.1.288.g0e0cd299f1-goog