[PATCH AUTOSEL 5.15 17/21] ila: block BH in ila_output()

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit cf28ff8e4c02e1ffa850755288ac954b6ff0db8c ]

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@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240531132636.2637995-5-edumazet@google.com (local)
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 8c1ce78956bae..9d37f7164e732 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);

-- 
2.43.0