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

[PATCH ipsec] 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/
---
 include/net/xfrm.h     | 10 ++-----
 net/xfrm/xfrm_policy.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 7 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 7d20776..c1c8493 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -994,6 +994,8 @@ 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 +1027,7 @@ 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_policy.c b/net/xfrm/xfrm_policy.c
index 7a23078..1da8a65 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);
+
+static void xfrm_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
@@ -2937,6 +2990,20 @@ static void xfrm_policy_fini(struct net *net)
 	xfrm_hash_free(net->xfrm.policy_byidx, sz);
 }
 
+static int xfrm_netdev_event(struct notifier_block *this, unsigned long event,
+			     void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+
+	if (event == NETDEV_UNREGISTER)
+		xfrm_flush_dev(dev);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block xfrm_netdev_notifier = {
+	.notifier_call = xfrm_netdev_event,
+};
+
 static int __net_init xfrm_net_init(struct net *net)
 {
 	int rv;
@@ -2984,6 +3051,19 @@ 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);
+	}
+	register_netdevice_notifier(&xfrm_netdev_notifier);
+}
+
 void __init xfrm_init(void)
 {
 	int i;
@@ -2998,6 +3078,7 @@ 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] net: xfrm_policy: fix device unregistration hang

[Shannon Nelson]

On 2/12/2018 9:21 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/
> ---
>   include/net/xfrm.h     | 10 ++-----
>   net/xfrm/xfrm_policy.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 84 insertions(+), 7 deletions(-)
> 
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index 7d20776..c1c8493 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -994,6 +994,8 @@ 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 +1027,7 @@ 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_policy.c b/net/xfrm/xfrm_policy.c
> index 7a23078..1da8a65 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);
> +
> +static void xfrm_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
> @@ -2937,6 +2990,20 @@ static void xfrm_policy_fini(struct net *net)
>   	xfrm_hash_free(net->xfrm.policy_byidx, sz);
>   }
>   
> +static int xfrm_netdev_event(struct notifier_block *this, unsigned long event,
> +			     void *ptr)
> +{
> +	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> +
> +	if (event == NETDEV_UNREGISTER)
> +		xfrm_flush_dev(dev);
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block xfrm_netdev_notifier = {
> +	.notifier_call = xfrm_netdev_event,
> +};
> +

Instead of creating yet another netdev notifier, can this be wired into 
xfrm_dev_unregister(), the existing notifier in xfrm_decide.c which 
calls into xfrm_policy_cache_flush()?

sln

>   static int __net_init xfrm_net_init(struct net *net)
>   {
>   	int rv;
> @@ -2984,6 +3051,19 @@ 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);
> +	}
> +	register_netdevice_notifier(&xfrm_netdev_notifier);
> +}
> +
>   void __init xfrm_init(void)
>   {
>   	int i;
> @@ -2998,6 +3078,7 @@ 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] net: xfrm_policy: fix device unregistration hang

[Eyal Birger]

On Mon, 12 Feb 2018 09:55:48 -0800
Shannon Nelson <shannon.nelson@oracle.com> wrote:

> On 2/12/2018 9:21 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/
> > ---
> >   include/net/xfrm.h     | 10 ++-----
> >   net/xfrm/xfrm_policy.c | 81
> > ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed,
> > 84 insertions(+), 7 deletions(-)
> > 
> > diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> > index 7d20776..c1c8493 100644
> > --- a/include/net/xfrm.h
> > +++ b/include/net/xfrm.h
> > @@ -994,6 +994,8 @@ 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 +1027,7 @@ 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_policy.c b/net/xfrm/xfrm_policy.c
> > index 7a23078..1da8a65 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);
> > +
> > +static void xfrm_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
> > @@ -2937,6 +2990,20 @@ static void xfrm_policy_fini(struct net *net)
> >   	xfrm_hash_free(net->xfrm.policy_byidx, sz);
> >   }
> >   
> > +static int xfrm_netdev_event(struct notifier_block *this, unsigned
> > long event,
> > +			     void *ptr)
> > +{
> > +	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> > +
> > +	if (event == NETDEV_UNREGISTER)
> > +		xfrm_flush_dev(dev);
> > +	return NOTIFY_DONE;
> > +}
> > +
> > +static struct notifier_block xfrm_netdev_notifier = {
> > +	.notifier_call = xfrm_netdev_event,
> > +};
> > +  
> 
> Instead of creating yet another netdev notifier, can this be wired
> into xfrm_dev_unregister(), the existing notifier in xfrm_decide.c
> which calls into xfrm_policy_cache_flush()?

I don't mind doing so... I was under the impression that xfrm_device.c
is designated to device offload (as indicated by the top level comment) -
though as you mentioned, xfrm_policy_cache_flush() is indeed called from
there.

Thanks!
Eyal.