Patch "ipv6: ioam: block BH from ioam6_output()" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    ipv6: ioam: block BH from ioam6_output()

to the 6.1-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:
     ipv6-ioam-block-bh-from-ioam6_output.patch
and it can be found in the queue-6.1 subdirectory.

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



commit 5577ffe3207905a9140ab94c02314b5ff386543e
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Fri May 31 13:26:32 2024 +0000

    ipv6: ioam: block BH from ioam6_output()
    
    [ Upstream commit 2fe40483ec257de2a0d819ef88e3e76c7e261319 ]
    
    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 ioam6_output() is not good enough,
    because ioam6_output() is called from process context,
    lwtunnel_output() only uses rcu_read_lock().
    
    We might be interrupted by a softirq, re-enter ioam6_output()
    and corrupt dst_cache data structures.
    
    Fix the race by using local_bh_disable() instead of
    preempt_disable().
    
    Fixes: 8cb3bf8bff3c ("ipv6: ioam: Add support for the ip6ip6 encapsulation")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Cc: Justin Iurman <justin.iurman@xxxxxxxxx>
    Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240531132636.2637995-2-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv6/ioam6_iptunnel.c b/net/ipv6/ioam6_iptunnel.c
index f6f5b83dd954d..a5cfc5b0b206b 100644
--- a/net/ipv6/ioam6_iptunnel.c
+++ b/net/ipv6/ioam6_iptunnel.c
@@ -351,9 +351,9 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 		goto drop;
 
 	if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {
-		preempt_disable();
+		local_bh_disable();
 		dst = dst_cache_get(&ilwt->cache);
-		preempt_enable();
+		local_bh_enable();
 
 		if (unlikely(!dst)) {
 			struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -373,9 +373,9 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 				goto drop;
 			}
 
-			preempt_disable();
+			local_bh_disable();
 			dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);
-			preempt_enable();
+			local_bh_enable();
 		}
 
 		skb_dst_drop(skb);