5.15-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit c0b98ac1cc104f48763cdb27b1e9ac25fd81fc90 ]
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 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: fa79581ea66c ("ipv6: sr: fix several BUGs when preemption is enabled") Fixes: 6c8702c60b88 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/seg6_iptunnel.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c index f98bb719190be..135712649d25f 100644 --- a/net/ipv6/seg6_iptunnel.c +++ b/net/ipv6/seg6_iptunnel.c @@ -332,9 +332,8 @@ 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();
skb_dst_drop(skb);
@@ -342,14 +341,13 @@ static int seg6_input_core(struct net *net, struct sock *sk, 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_set(skb, dst); } + local_bh_enable();
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); if (unlikely(err)) @@ -405,9 +403,9 @@ 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); @@ -427,9 +425,9 @@ 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);