[PATCH ipsec,v2] net: xfrm_policy: fix device unregistration hang

[PATCH ipsec,v2] net: xfrm_policy: fix device unregistration hang

[Eyal Birger]

In setups like the following:

       Host A          --        Host B
tun0 -- ipsec -- eth0  --  eth0 -- ipsec -- tun0

where tun0 are tunnel devices using dst_cache (ipip, ipip6, etc...).

Unregistration of an underlying eth0 device leads to the following log
messages:

unregister_netdevice: waiting for eth0 to become free. Usage count = 2

This is since xfrm dsts device references are not released upon device
unregistration when the xfrm dst is cached in a dst_cache.

Several approaches for fixing this were discussed in [1]; this commit keeps
track of allocated xdsts and releases their device references on a netdev
unregister event.

Signed-off-by: Eyal Birger <eyal.birger@gmail.com>

[1] https://patchwork.ozlabs.org/patch/869025/

---

v2:
  - call gc flush from existing netdev notifier per Shannon Nelson's
    suggestion.
---
 include/net/xfrm.h     | 11 +++------
 net/xfrm/xfrm_device.c |  2 ++
 net/xfrm/xfrm_policy.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+), 7 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 7d20776..4614047 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -324,6 +324,7 @@ void xfrm_policy_unregister_afinfo(const struct xfrm_policy_afinfo *afinfo);
 void km_policy_notify(struct xfrm_policy *xp, int dir,
 		      const struct km_event *c);
 void xfrm_policy_cache_flush(void);
+void xfrm_policy_dst_gc_flush_dev(struct net_device *dev);
 void km_state_notify(struct xfrm_state *x, const struct km_event *c);
 
 struct xfrm_tmpl;
@@ -994,6 +995,8 @@ struct xfrm_dst {
 	u32 child_mtu_cached;
 	u32 route_cookie;
 	u32 path_cookie;
+	struct list_head xfrm_dst_gc;
+	struct xfrm_dst_list *xfrm_dst_gc_list;
 };
 
 static inline struct dst_entry *xfrm_dst_path(const struct dst_entry *dst)
@@ -1025,13 +1028,7 @@ static inline void xfrm_dst_set_child(struct xfrm_dst *xdst, struct dst_entry *c
 	xdst->child = child;
 }
 
-static inline void xfrm_dst_destroy(struct xfrm_dst *xdst)
-{
-	xfrm_pols_put(xdst->pols, xdst->num_pols);
-	dst_release(xdst->route);
-	if (likely(xdst->u.dst.xfrm))
-		xfrm_state_put(xdst->u.dst.xfrm);
-}
+void xfrm_dst_destroy(struct xfrm_dst *xdst);
 #endif
 
 void xfrm_dst_ifdown(struct dst_entry *dst, struct net_device *dev);
diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
index 8e70291..5bd9892 100644
--- a/net/xfrm/xfrm_device.c
+++ b/net/xfrm/xfrm_device.c
@@ -309,6 +309,7 @@ static int xfrm_dev_register(struct net_device *dev)
 static int xfrm_dev_unregister(struct net_device *dev)
 {
 	xfrm_policy_cache_flush();
+	xfrm_policy_dst_gc_flush_dev(dev);
 	return NOTIFY_DONE;
 }
 
@@ -323,6 +324,7 @@ static int xfrm_dev_down(struct net_device *dev)
 		xfrm_dev_state_flush(dev_net(dev), dev, true);
 
 	xfrm_policy_cache_flush();
+	xfrm_policy_dst_gc_flush_dev(dev);
 	return NOTIFY_DONE;
 }
 
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 7a23078..c7b9a9a 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -45,6 +45,12 @@ struct xfrm_flo {
 	u8 flags;
 };
 
+struct xfrm_dst_list {
+	spinlock_t lock; /* sync writers */
+	struct list_head head;
+};
+
+static DEFINE_PER_CPU_ALIGNED(struct xfrm_dst_list, xfrm_dst_gc_list);
 static DEFINE_PER_CPU(struct xfrm_dst *, xfrm_last_dst);
 static struct work_struct *xfrm_pcpu_work __read_mostly;
 static DEFINE_SPINLOCK(xfrm_policy_afinfo_lock);
@@ -94,6 +100,51 @@ __xfrm6_selector_match(const struct xfrm_selector *sel, const struct flowi *fl)
 		(fl6->flowi6_oif == sel->ifindex || !sel->ifindex);
 }
 
+static void xfrm_dst_add_to_gc_list(struct xfrm_dst *xdst)
+{
+	struct xfrm_dst_list *xl = raw_cpu_ptr(&xfrm_dst_gc_list);
+
+	xdst->xfrm_dst_gc_list = xl;
+
+	spin_lock_bh(&xl->lock);
+	list_add_tail(&xdst->xfrm_dst_gc, &xl->head);
+	spin_unlock_bh(&xl->lock);
+}
+
+void xfrm_dst_destroy(struct xfrm_dst *xdst)
+{
+	xfrm_pols_put(xdst->pols, xdst->num_pols);
+	dst_release(xdst->route);
+	if (likely(xdst->u.dst.xfrm))
+		xfrm_state_put(xdst->u.dst.xfrm);
+	if (!list_empty(&xdst->xfrm_dst_gc)) {
+		struct xfrm_dst_list *xl = xdst->xfrm_dst_gc_list;
+
+		spin_lock_bh(&xl->lock);
+		list_del(&xdst->xfrm_dst_gc);
+		spin_unlock_bh(&xl->lock);
+	}
+}
+EXPORT_SYMBOL_GPL(xfrm_dst_destroy);
+
+void xfrm_policy_dst_gc_flush_dev(struct net_device *dev)
+{
+	struct xfrm_dst *xdst;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct xfrm_dst_list *xl = &per_cpu(xfrm_dst_gc_list, cpu);
+
+		spin_lock_bh(&xl->lock);
+		list_for_each_entry(xdst, &xl->head, xfrm_dst_gc) {
+			if (xdst->u.dst.dev != dev)
+				continue;
+			dst_dev_put(&xdst->u.dst);
+		}
+		spin_unlock_bh(&xl->lock);
+	}
+}
+
 bool xfrm_selector_match(const struct xfrm_selector *sel, const struct flowi *fl,
 			 unsigned short family)
 {
@@ -1581,6 +1632,8 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
 		}
 
 		bundle[i] = xdst;
+		xfrm_dst_add_to_gc_list(xdst);
+
 		if (!xdst_prev)
 			xdst0 = xdst;
 		else
@@ -2984,6 +3037,18 @@ static struct pernet_operations __net_initdata xfrm_net_ops = {
 	.exit = xfrm_net_exit,
 };
 
+static void __init xfrm_dst_gc_init(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct xfrm_dst_list *xl = &per_cpu(xfrm_dst_gc_list, cpu);
+
+		INIT_LIST_HEAD(&xl->head);
+		spin_lock_init(&xl->lock);
+	}
+}
+
 void __init xfrm_init(void)
 {
 	int i;
@@ -2998,6 +3063,7 @@ void __init xfrm_init(void)
 	register_pernet_subsys(&xfrm_net_ops);
 	seqcount_init(&xfrm_policy_hash_generation);
 	xfrm_input_init();
+	xfrm_dst_gc_init();
 }
 
 #ifdef CONFIG_AUDITSYSCALL
-- 
2.7.4

Re: [PATCH ipsec,v2] net: xfrm_policy: fix device unregistration hang

[Shannon Nelson]

On 2/12/2018 10:58 AM, Eyal Birger wrote:
> In setups like the following:
> 
>         Host A          --        Host B
> tun0 -- ipsec -- eth0  --  eth0 -- ipsec -- tun0
> 
> where tun0 are tunnel devices using dst_cache (ipip, ipip6, etc...).
> 
> Unregistration of an underlying eth0 device leads to the following log
> messages:
> 
> unregister_netdevice: waiting for eth0 to become free. Usage count = 2
> 
> This is since xfrm dsts device references are not released upon device
> unregistration when the xfrm dst is cached in a dst_cache.
> 
> Several approaches for fixing this were discussed in [1]; this commit keeps
> track of allocated xdsts and releases their device references on a netdev
> unregister event.
> 
> Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
> 
> [1] https://patchwork.ozlabs.org/patch/869025/
> 
> ---
> 
> v2:
>    - call gc flush from existing netdev notifier per Shannon Nelson's
>      suggestion.

Acked-by: Shannon Nelson <shannon.nelson@oracle.com>

> ---
>   include/net/xfrm.h     | 11 +++------
>   net/xfrm/xfrm_device.c |  2 ++
>   net/xfrm/xfrm_policy.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 72 insertions(+), 7 deletions(-)
> 
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index 7d20776..4614047 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -324,6 +324,7 @@ void xfrm_policy_unregister_afinfo(const struct xfrm_policy_afinfo *afinfo);
>   void km_policy_notify(struct xfrm_policy *xp, int dir,
>   		      const struct km_event *c);
>   void xfrm_policy_cache_flush(void);
> +void xfrm_policy_dst_gc_flush_dev(struct net_device *dev);
>   void km_state_notify(struct xfrm_state *x, const struct km_event *c);
>   
>   struct xfrm_tmpl;
> @@ -994,6 +995,8 @@ struct xfrm_dst {
>   	u32 child_mtu_cached;
>   	u32 route_cookie;
>   	u32 path_cookie;
> +	struct list_head xfrm_dst_gc;
> +	struct xfrm_dst_list *xfrm_dst_gc_list;
>   };
>   
>   static inline struct dst_entry *xfrm_dst_path(const struct dst_entry *dst)
> @@ -1025,13 +1028,7 @@ static inline void xfrm_dst_set_child(struct xfrm_dst *xdst, struct dst_entry *c
>   	xdst->child = child;
>   }
>   
> -static inline void xfrm_dst_destroy(struct xfrm_dst *xdst)
> -{
> -	xfrm_pols_put(xdst->pols, xdst->num_pols);
> -	dst_release(xdst->route);
> -	if (likely(xdst->u.dst.xfrm))
> -		xfrm_state_put(xdst->u.dst.xfrm);
> -}
> +void xfrm_dst_destroy(struct xfrm_dst *xdst);
>   #endif
>   
>   void xfrm_dst_ifdown(struct dst_entry *dst, struct net_device *dev);
> diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
> index 8e70291..5bd9892 100644
> --- a/net/xfrm/xfrm_device.c
> +++ b/net/xfrm/xfrm_device.c
> @@ -309,6 +309,7 @@ static int xfrm_dev_register(struct net_device *dev)
>   static int xfrm_dev_unregister(struct net_device *dev)
>   {
>   	xfrm_policy_cache_flush();
> +	xfrm_policy_dst_gc_flush_dev(dev);
>   	return NOTIFY_DONE;
>   }
>   
> @@ -323,6 +324,7 @@ static int xfrm_dev_down(struct net_device *dev)
>   		xfrm_dev_state_flush(dev_net(dev), dev, true);
>   
>   	xfrm_policy_cache_flush();
> +	xfrm_policy_dst_gc_flush_dev(dev);
>   	return NOTIFY_DONE;
>   }
>   
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index 7a23078..c7b9a9a 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -45,6 +45,12 @@ struct xfrm_flo {
>   	u8 flags;
>   };
>   
> +struct xfrm_dst_list {
> +	spinlock_t lock; /* sync writers */
> +	struct list_head head;
> +};
> +
> +static DEFINE_PER_CPU_ALIGNED(struct xfrm_dst_list, xfrm_dst_gc_list);
>   static DEFINE_PER_CPU(struct xfrm_dst *, xfrm_last_dst);
>   static struct work_struct *xfrm_pcpu_work __read_mostly;
>   static DEFINE_SPINLOCK(xfrm_policy_afinfo_lock);
> @@ -94,6 +100,51 @@ __xfrm6_selector_match(const struct xfrm_selector *sel, const struct flowi *fl)
>   		(fl6->flowi6_oif == sel->ifindex || !sel->ifindex);
>   }
>   
> +static void xfrm_dst_add_to_gc_list(struct xfrm_dst *xdst)
> +{
> +	struct xfrm_dst_list *xl = raw_cpu_ptr(&xfrm_dst_gc_list);
> +
> +	xdst->xfrm_dst_gc_list = xl;
> +
> +	spin_lock_bh(&xl->lock);
> +	list_add_tail(&xdst->xfrm_dst_gc, &xl->head);
> +	spin_unlock_bh(&xl->lock);
> +}
> +
> +void xfrm_dst_destroy(struct xfrm_dst *xdst)
> +{
> +	xfrm_pols_put(xdst->pols, xdst->num_pols);
> +	dst_release(xdst->route);
> +	if (likely(xdst->u.dst.xfrm))
> +		xfrm_state_put(xdst->u.dst.xfrm);
> +	if (!list_empty(&xdst->xfrm_dst_gc)) {
> +		struct xfrm_dst_list *xl = xdst->xfrm_dst_gc_list;
> +
> +		spin_lock_bh(&xl->lock);
> +		list_del(&xdst->xfrm_dst_gc);
> +		spin_unlock_bh(&xl->lock);
> +	}
> +}
> +EXPORT_SYMBOL_GPL(xfrm_dst_destroy);
> +
> +void xfrm_policy_dst_gc_flush_dev(struct net_device *dev)
> +{
> +	struct xfrm_dst *xdst;
> +	int cpu;
> +
> +	for_each_possible_cpu(cpu) {
> +		struct xfrm_dst_list *xl = &per_cpu(xfrm_dst_gc_list, cpu);
> +
> +		spin_lock_bh(&xl->lock);
> +		list_for_each_entry(xdst, &xl->head, xfrm_dst_gc) {
> +			if (xdst->u.dst.dev != dev)
> +				continue;
> +			dst_dev_put(&xdst->u.dst);
> +		}
> +		spin_unlock_bh(&xl->lock);
> +	}
> +}
> +
>   bool xfrm_selector_match(const struct xfrm_selector *sel, const struct flowi *fl,
>   			 unsigned short family)
>   {
> @@ -1581,6 +1632,8 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
>   		}
>   
>   		bundle[i] = xdst;
> +		xfrm_dst_add_to_gc_list(xdst);
> +
>   		if (!xdst_prev)
>   			xdst0 = xdst;
>   		else
> @@ -2984,6 +3037,18 @@ static struct pernet_operations __net_initdata xfrm_net_ops = {
>   	.exit = xfrm_net_exit,
>   };
>   
> +static void __init xfrm_dst_gc_init(void)
> +{
> +	int cpu;
> +
> +	for_each_possible_cpu(cpu) {
> +		struct xfrm_dst_list *xl = &per_cpu(xfrm_dst_gc_list, cpu);
> +
> +		INIT_LIST_HEAD(&xl->head);
> +		spin_lock_init(&xl->lock);
> +	}
> +}
> +
>   void __init xfrm_init(void)
>   {
>   	int i;
> @@ -2998,6 +3063,7 @@ void __init xfrm_init(void)
>   	register_pernet_subsys(&xfrm_net_ops);
>   	seqcount_init(&xfrm_policy_hash_generation);
>   	xfrm_input_init();
> +	xfrm_dst_gc_init();
>   }
>   
>   #ifdef CONFIG_AUDITSYSCALL
> 

Re: [PATCH ipsec,v2] net: xfrm_policy: fix device unregistration hang

[Steffen Klassert]

On Mon, Feb 12, 2018 at 08:58:28PM +0200, Eyal Birger wrote:
> In setups like the following:
> 
>        Host A          --        Host B
> tun0 -- ipsec -- eth0  --  eth0 -- ipsec -- tun0
> 
> where tun0 are tunnel devices using dst_cache (ipip, ipip6, etc...).
> 
> Unregistration of an underlying eth0 device leads to the following log
> messages:
> 
> unregister_netdevice: waiting for eth0 to become free. Usage count = 2
> 
> This is since xfrm dsts device references are not released upon device
> unregistration when the xfrm dst is cached in a dst_cache.
> 
> Several approaches for fixing this were discussed in [1]; this commit keeps
> track of allocated xdsts and releases their device references on a netdev
> unregister event.
> 
> Signed-off-by: Eyal Birger <eyal.birger@gmail.com>

Please add a 'Fixes' tag, it is not so clear what introduced this bug.