net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

[ Upstream commit 92191dd1073088753821b862b791dcc83e558e07 ]

Some lwtunnels have a dst cache for post-transformation dst.
If the packet destination did not change we may end up recording
a reference to the lwtunnel in its own cache, and the lwtunnel
state will never be freed.

Discovered by the ioam6.sh test, kmemleak was recently fixed
to catch per-cpu memory leaks. I'm not sure if rpl and seg6
can actually hit this, but in principle I don't see why not.

Fixes: 8cb3bf8bff3c ("ipv6: ioam: Add support for the ip6ip6 encapsulation")
Fixes: 6c8702c60b88 ("ipv6: sr: add support for SRH encapsulation and injection with lwtunnels")
Fixes: a7a29f9c361f ("net: ipv6: add rpl sr tunnel")
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250130031519.2716843-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv6/ioam6_iptunnel.c b/net/ipv6/ioam6_iptunnel.c
index e81b45b1f655572b5562ad3403d44404754c4aa1..fb6cb540cd1bc82f4fd1ef3c553715af7c81648d 100644 (file)
--- a/net/ipv6/ioam6_iptunnel.c
+++ b/net/ipv6/ioam6_iptunnel.c
@@ -413,9 +413,12 @@ do_encap:
                        goto drop;
                }
 
-               local_bh_disable();
-               dst_cache_set_ip6(&ilwt->cache, cache_dst, &fl6.saddr);
-               local_bh_enable();
+               /* cache only if we don't create a dst reference loop */
+               if (dst->lwtstate != cache_dst->lwtstate) {
+                       local_bh_disable();
+                       dst_cache_set_ip6(&ilwt->cache, cache_dst, &fl6.saddr);
+                       local_bh_enable();
+               }
 
                err = skb_cow_head(skb, LL_RESERVED_SPACE(cache_dst->dev));
                if (unlikely(err))

diff --git a/net/ipv6/rpl_iptunnel.c b/net/ipv6/rpl_iptunnel.c
index 7ba22d2f2bfefa73a9fcaed0fab50d8a5afc1cad..be084089ec783a9ce735e98518e2bda730e5fa19 100644 (file)
--- a/net/ipv6/rpl_iptunnel.c
+++ b/net/ipv6/rpl_iptunnel.c
@@ -236,9 +236,12 @@ static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
                        goto drop;
                }
 
-               local_bh_disable();
-               dst_cache_set_ip6(&rlwt->cache, dst, &fl6.saddr);
-               local_bh_enable();
+               /* cache only if we don't create a dst reference loop */
+               if (orig_dst->lwtstate != dst->lwtstate) {
+                       local_bh_disable();
+                       dst_cache_set_ip6(&rlwt->cache, dst, &fl6.saddr);
+                       local_bh_enable();
+               }
 
                err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
                if (unlikely(err))

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index 4bf937bfc2633c6abad8249e6ffae6c67070d7a9..316dbc2694f2aa1d4434ffc4290b1edaafbcb8f2 100644 (file)
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -575,9 +575,12 @@ static int seg6_output_core(struct net *net, struct sock *sk,
                        goto drop;
                }
 
-               local_bh_disable();
-               dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
-               local_bh_enable();
+               /* cache only if we don't create a dst reference loop */
+               if (orig_dst->lwtstate != dst->lwtstate) {
+                       local_bh_disable();
+                       dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
+                       local_bh_enable();
+               }
 
                err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
                if (unlikely(err))