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@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240531132636.2637995-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/ila/ila_lwt.c b/net/ipv6/ila/ila_lwt.c
index 0601bad..ff7e734 100644 (file)
--- 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);