[PATCH AUTOSEL 5.10 08/13] net: ipv6: rpl_iptunnel: block BH in rpl_output() and rpl_input()

Sasha Levin
2024-06-18T12:42:45Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit db0090c6eb12c31246438b7fe2a8f1b833e7a653 ]

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 rpl_output() is not good enough,
because rpl_output() is called from process context,
lwtunnel_output() only uses rcu_read_lock().

We might be interrupted by a softirq, re-enter rpl_output()
and corrupt dst_cache data structures.

Fix the race by using local_bh_disable() instead of
preempt_disable().

Apply a similar change in rpl_input().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexander Aring <aahringo@redhat.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240531132636.2637995-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/rpl_iptunnel.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/rpl_iptunnel.c b/net/ipv6/rpl_iptunnel.c
index 5fdf3ebb953fb..2ba605db69769 100644
--- a/net/ipv6/rpl_iptunnel.c
+++ b/net/ipv6/rpl_iptunnel.c
@@ -217,9 +217,9 @@ static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
if (unlikely(err))
goto drop;

- preempt_disable();
+ local_bh_disable();
dst = dst_cache_get(&rlwt->cache);
- preempt_enable();
+ local_bh_enable();

if (unlikely(!dst)) {
struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -239,9 +239,9 @@ static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
goto drop;
}

- preempt_disable();
+ local_bh_disable();
dst_cache_set_ip6(&rlwt->cache, dst, &fl6.saddr);
- preempt_enable();
+ local_bh_enable();
}

skb_dst_drop(skb);
@@ -273,9 +273,8 @@ static int rpl_input(struct sk_buff *skb)
return err;
}

- preempt_disable();
+ local_bh_disable();
dst = dst_cache_get(&rlwt->cache);
- preempt_enable();

skb_dst_drop(skb);

@@ -283,14 +282,13 @@ static int rpl_input(struct sk_buff *skb)
ip6_route_input(skb);
dst = skb_dst(skb);
if (!dst->error) {
- preempt_disable();
dst_cache_set_ip6(&rlwt->cache, dst,
&ipv6_hdr(skb)->saddr);
- preempt_enable();
}
} else {
skb_dst_set(skb, dst);
}
+ local_bh_enable();

err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
--
2.43.0