From 2fe40483ec257de2a0d819ef88e3e76c7e261319 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 31 May 2024 13:26:32 +0000 Subject: [PATCH 1/5] ipv6: ioam: block BH from ioam6_output() 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 Cc: Justin Iurman Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240531132636.2637995-2-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv6/ioam6_iptunnel.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv6/ioam6_iptunnel.c b/net/ipv6/ioam6_iptunnel.c index 7563f8c6aa87..bf7120ecea1e 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); From db0090c6eb12c31246438b7fe2a8f1b833e7a653 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 31 May 2024 13:26:33 +0000 Subject: [PATCH 2/5] net: ipv6: rpl_iptunnel: block BH in rpl_output() and rpl_input() 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 Cc: Alexander Aring Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240531132636.2637995-3-edumazet@google.com Signed-off-by: Jakub Kicinski --- 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 a013b92cbb86..2c83b7586422 100644 --- a/net/ipv6/rpl_iptunnel.c +++ b/net/ipv6/rpl_iptunnel.c @@ -212,9 +212,9 @@ 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); @@ -234,9 +234,9 @@ 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); @@ -268,23 +268,21 @@ static int rpl_input(struct sk_buff *skb) return err; } - preempt_disable(); + local_bh_disable(); dst = dst_cache_get(&rlwt->cache); - preempt_enable(); if (!dst) { 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_drop(skb); skb_dst_set(skb, dst); } + local_bh_enable(); err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); if (unlikely(err)) From c0b98ac1cc104f48763cdb27b1e9ac25fd81fc90 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 31 May 2024 13:26:34 +0000 Subject: [PATCH 3/5] ipv6: sr: block BH in seg6_output_core() and seg6_input_core() 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 Cc: David Lebrun Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240531132636.2637995-4-edumazet@google.com Signed-off-by: Jakub Kicinski --- 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 a75df2ec8db0..098632adc9b5 100644 --- a/net/ipv6/seg6_iptunnel.c +++ b/net/ipv6/seg6_iptunnel.c @@ -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); From cf28ff8e4c02e1ffa850755288ac954b6ff0db8c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 31 May 2024 13:26:35 +0000 Subject: [PATCH 4/5] ila: block BH in ila_output() 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. ila_output() is called from lwtunnel_output() possibly from process context, and under rcu_read_lock(). We might be interrupted by a softirq, re-enter ila_output() and corrupt dst_cache data structures. Fix the race by using local_bh_disable(). Signed-off-by: Eric Dumazet Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240531132636.2637995-5-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv6/ila/ila_lwt.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/ipv6/ila/ila_lwt.c b/net/ipv6/ila/ila_lwt.c index 0601bad79822..ff7e734e335b 100644 --- a/net/ipv6/ila/ila_lwt.c +++ b/net/ipv6/ila/ila_lwt.c @@ -58,7 +58,9 @@ static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb) return orig_dst->lwtstate->orig_output(net, sk, skb); } + local_bh_disable(); dst = dst_cache_get(&ilwt->dst_cache); + local_bh_enable(); if (unlikely(!dst)) { struct ipv6hdr *ip6h = ipv6_hdr(skb); struct flowi6 fl6; @@ -86,8 +88,11 @@ static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb) goto drop; } - if (ilwt->connected) + if (ilwt->connected) { + local_bh_disable(); dst_cache_set_ip6(&ilwt->dst_cache, dst, &fl6.saddr); + local_bh_enable(); + } } skb_dst_set(skb, dst); From 2fe6fb36c781b50482b1c3323fb526bc07d1af59 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 31 May 2024 13:26:36 +0000 Subject: [PATCH 5/5] net: dst_cache: add two DEBUG_NET warnings After fixing four different bugs involving dst_cache users, it might be worth adding a check about BH being blocked by dst_cache callers. DEBUG_NET_WARN_ON_ONCE(!in_softirq()); It is not fatal, if we missed valid case where no BH deadlock is to be feared, we might change this. Signed-off-by: Eric Dumazet Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240531132636.2637995-6-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/core/dst_cache.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/core/dst_cache.c b/net/core/dst_cache.c index 6a0482e676d3..70c634b9e7b0 100644 --- a/net/core/dst_cache.c +++ b/net/core/dst_cache.c @@ -27,6 +27,7 @@ struct dst_cache_pcpu { static void dst_cache_per_cpu_dst_set(struct dst_cache_pcpu *dst_cache, struct dst_entry *dst, u32 cookie) { + DEBUG_NET_WARN_ON_ONCE(!in_softirq()); dst_release(dst_cache->dst); if (dst) dst_hold(dst); @@ -40,6 +41,7 @@ static struct dst_entry *dst_cache_per_cpu_get(struct dst_cache *dst_cache, { struct dst_entry *dst; + DEBUG_NET_WARN_ON_ONCE(!in_softirq()); dst = idst->dst; if (!dst) goto fail;