Patch "ila: block BH in ila_output()" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ila: block BH in ila_output()

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ila-block-bh-in-ila_output.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a262d3c07aac94db8db764a17409e3316cd32ad4
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Fri May 31 13:26:35 2024 +0000

    ila: block BH in ila_output()
    
    [ 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@xxxxxxxxxx>
    Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240531132636.2637995-5-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv6/ila/ila_lwt.c b/net/ipv6/ila/ila_lwt.c
index 0601bad798221..ff7e734e335b0 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);