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ipv6: sr: block BH in seg6_output_core() and seg6_input_core()

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As explained in commit 1378817486 ("tipc: block BH
before using dst_cache"), net/core/dst_cache.c
helpers need to be called with BH disabled.

Disabling preemption in seg6_output_core() is not good enough,
because seg6_output_core() is called from process context,
lwtunnel_output() only uses rcu_read_lock().

We might be interrupted by a softirq, re-enter seg6_output_core()
and corrupt dst_cache data structures.

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

Apply a similar change in seg6_input_core().

Fixes: fa79581ea6 ("ipv6: sr: fix several BUGs when preemption is enabled")
Fixes: 6c8702c60b ("ipv6: sr: add support for SRH encapsulation and injection with lwtunnels")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Lebrun <dlebrun@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240531132636.2637995-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2024-05-31 13:26:34 +00:00 committed by Jakub Kicinski
parent db0090c6eb
commit c0b98ac1cc
1 changed files with 6 additions and 8 deletions
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14
net/ipv6/seg6_iptunnel.c
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@ -464,23 +464,21 @@ static int seg6_input_core(struct net *net, struct sock *sk,
slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
preempt_disable();
local_bh_disable();
dst = dst_cache_get(&slwt->cache);
preempt_enable();
if (!dst) {
ip6_route_input(skb);
dst = skb_dst(skb);
if (!dst->error) {
preempt_disable();
dst_cache_set_ip6(&slwt->cache, dst,
&ipv6_hdr(skb)->saddr);
preempt_enable();
}
} else {
skb_dst_drop(skb);
skb_dst_set(skb, dst);
}
local_bh_enable();
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
@ -536,9 +534,9 @@ static int seg6_output_core(struct net *net, struct sock *sk,
slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
preempt_disable();
local_bh_disable();
dst = dst_cache_get(&slwt->cache);
preempt_enable();
local_bh_enable();
if (unlikely(!dst)) {
struct ipv6hdr *hdr = ipv6_hdr(skb);
@ -558,9 +556,9 @@ static int seg6_output_core(struct net *net, struct sock *sk,
goto drop;
}
preempt_disable();
local_bh_disable();
dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
preempt_enable();
local_bh_enable();
}
skb_dst_drop(skb);