[PATCH v3] kernel: fix scheduling while atomic in bridge offload
Qingfang DENG
dqfext at gmail.com
Mon May 15 03:26:40 PDT 2023
From: Qingfang DENG <qingfang.deng at siflower.com.cn>
br_offload_port_state is in a spinlock's critical section (&br->lock),
but rhashtable_init/rhashtable_free_and_destroy/flush_work may sleep,
causing scheduling while atomic bug.
To fix this, use workqueues to defer the init/destroy operations. To
synchronize between rhashtable insert/destroy, synchronize_rcu is used
to ensure all writers have left the RCU critical section before calling
rhashtable_free_and_destroy.
While at it, check for null pointers at the flow allocation.
Fixes: 94b4da9b4aad ("kernel: add a fast path for the bridge code")
Signed-off-by: Qingfang DENG <qingfang.deng at siflower.com.cn>
---
v3: fix race conditions and optimize code
.../hack-5.15/600-bridge_offload.patch | 97 +++++++++++++------
1 file changed, 69 insertions(+), 28 deletions(-)
diff --git a/target/linux/generic/hack-5.15/600-bridge_offload.patch b/target/linux/generic/hack-5.15/600-bridge_offload.patch
index 9d71a741b2..87396611bd 100644
--- a/target/linux/generic/hack-5.15/600-bridge_offload.patch
+++ b/target/linux/generic/hack-5.15/600-bridge_offload.patch
@@ -150,16 +150,25 @@ Subject: [PATCH] net/bridge: add bridge offload
/*
* Determine initial path cost based on speed.
-@@ -428,7 +429,7 @@ static struct net_bridge_port *new_nbp(s
+@@ -362,6 +363,7 @@ static void del_nbp(struct net_bridge_po
+ kobject_del(&p->kobj);
+
+ br_netpoll_disable(p);
++ flush_work(&p->offload.deferred_work);
+
+ call_rcu(&p->rcu, destroy_nbp_rcu);
+ }
+@@ -428,7 +430,8 @@ static struct net_bridge_port *new_nbp(s
p->path_cost = port_cost(dev);
p->priority = 0x8000 >> BR_PORT_BITS;
p->port_no = index;
- p->flags = BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD | BR_BCAST_FLOOD;
+ p->flags = BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD | BR_BCAST_FLOOD | BR_OFFLOAD;
++ br_offload_init_work(p);
br_init_port(p);
br_set_state(p, BR_STATE_DISABLED);
br_stp_port_timer_init(p);
-@@ -771,6 +772,9 @@ void br_port_flags_change(struct net_bri
+@@ -771,6 +774,9 @@ void br_port_flags_change(struct net_bri
if (mask & BR_NEIGH_SUPPRESS)
br_recalculate_neigh_suppress_enabled(br);
@@ -199,7 +208,7 @@ Subject: [PATCH] net/bridge: add bridge offload
--- /dev/null
+++ b/net/bridge/br_offload.c
-@@ -0,0 +1,438 @@
+@@ -0,0 +1,458 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kernel.h>
+#include <linux/workqueue.h>
@@ -306,7 +315,7 @@ Subject: [PATCH] net/bridge: add bridge offload
+ p->br->offload_cache_reserved) >= p->br->offload_cache_size;
+}
+
-+static void
++void
+br_offload_gc_work(struct work_struct *work)
+{
+ struct rhashtable_iter hti;
@@ -354,36 +363,53 @@ Subject: [PATCH] net/bridge: add bridge offload
+
+}
+
-+void br_offload_port_state(struct net_bridge_port *p)
++void br_offload_deferred_work(struct work_struct *work)
+{
-+ struct net_bridge_port_offload *o = &p->offload;
-+ bool enabled = true;
-+ bool flush = false;
++ struct net_bridge_port_offload *o;
++ struct net_bridge_port *p;
++ bool enabling, enabled;
+
-+ if (p->state != BR_STATE_FORWARDING ||
-+ !(p->flags & BR_OFFLOAD))
-+ enabled = false;
++ p = container_of(work, struct net_bridge_port, offload.deferred_work);
++ o = &p->offload;
+
-+ spin_lock_bh(&offload_lock);
-+ if (o->enabled == enabled)
-+ goto out;
++ spin_lock_bh(&p->br->lock);
++ enabling = o->enabling;
++ enabled = o->enabled;
++ spin_unlock_bh(&p->br->lock);
++
++ if (enabling == enabled)
++ return;
+
-+ if (enabled) {
-+ if (!o->gc_work.func)
-+ INIT_WORK(&o->gc_work, br_offload_gc_work);
++ if (enabling) {
+ rhashtable_init(&o->rht, &flow_params);
++ spin_lock_bh(&offload_lock);
++ o->enabled = true;
++ spin_unlock_bh(&offload_lock);
+ } else {
-+ flush = true;
++ spin_lock_bh(&offload_lock);
++ o->enabled = false;
++ spin_unlock_bh(&offload_lock);
++ /* Ensure all rht users have finished */
++ synchronize_rcu();
++ cancel_work_sync(&o->gc_work);
+ rhashtable_free_and_destroy(&o->rht, br_offload_destroy_cb, o);
+ }
++}
+
-+ o->enabled = enabled;
++void br_offload_port_state(struct net_bridge_port *p)
++{
++ struct net_bridge_port_offload *o = &p->offload;
++ bool enabling = true;
+
-+out:
-+ spin_unlock_bh(&offload_lock);
++ if (p->state != BR_STATE_FORWARDING ||
++ !(p->flags & BR_OFFLOAD))
++ enabling = false;
++
++ if (o->enabling == enabling)
++ return;
+
-+ if (flush)
-+ flush_work(&o->gc_work);
++ o->enabling = enabling;
++ schedule_work(&o->deferred_work);
+}
+
+void br_offload_fdb_update(const struct net_bridge_fdb_entry *fdb)
@@ -475,6 +501,9 @@ Subject: [PATCH] net/bridge: add bridge offload
+#endif
+
+ flow = kmem_cache_alloc(offload_cache, GFP_ATOMIC);
++ if (unlikely(!flow))
++ goto out;
++
+ flow->port = inp;
+ memcpy(&flow->key, &key, sizeof(key));
+
@@ -655,20 +684,22 @@ Subject: [PATCH] net/bridge: add bridge offload
};
#define MDB_PG_FLAGS_PERMANENT BIT(0)
-@@ -343,6 +349,12 @@ struct net_bridge_mdb_entry {
+@@ -343,6 +349,14 @@ struct net_bridge_mdb_entry {
struct rcu_head rcu;
};
+struct net_bridge_port_offload {
+ struct rhashtable rht;
+ struct work_struct gc_work;
++ struct work_struct deferred_work;
+ bool enabled;
++ bool enabling;
+};
+
struct net_bridge_port {
struct net_bridge *br;
struct net_device *dev;
-@@ -403,6 +415,7 @@ struct net_bridge_port {
+@@ -403,6 +417,7 @@ struct net_bridge_port {
u16 backup_redirected_cnt;
struct bridge_stp_xstats stp_xstats;
@@ -676,7 +707,7 @@ Subject: [PATCH] net/bridge: add bridge offload
};
#define kobj_to_brport(obj) container_of(obj, struct net_bridge_port, kobj)
-@@ -519,6 +532,9 @@ struct net_bridge {
+@@ -519,6 +534,9 @@ struct net_bridge {
struct kobject *ifobj;
u32 auto_cnt;
@@ -686,7 +717,7 @@ Subject: [PATCH] net/bridge: add bridge offload
#ifdef CONFIG_NET_SWITCHDEV
/* Counter used to make sure that hardware domains get unique
* identifiers in case a bridge spans multiple switchdev instances.
-@@ -553,6 +569,10 @@ struct br_input_skb_cb {
+@@ -553,6 +571,10 @@ struct br_input_skb_cb {
#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
u8 br_netfilter_broute:1;
#endif
@@ -699,7 +730,7 @@ Subject: [PATCH] net/bridge: add bridge offload
/* Set if TX data plane offloading is used towards at least one
--- /dev/null
+++ b/net/bridge/br_private_offload.h
-@@ -0,0 +1,23 @@
+@@ -0,0 +1,33 @@
+#ifndef __BR_OFFLOAD_H
+#define __BR_OFFLOAD_H
+
@@ -713,6 +744,16 @@ Subject: [PATCH] net/bridge: add bridge offload
+ struct netlink_ext_ack *extack);
+int br_offload_set_cache_reserved(struct net_bridge *br, unsigned long val,
+ struct netlink_ext_ack *extack);
++void br_offload_deferred_work(struct work_struct *work);
++void br_offload_gc_work(struct work_struct *work);
++
++static inline void br_offload_init_work(struct net_bridge_port *p)
++{
++ struct net_bridge_port_offload *o = &p->offload;
++
++ INIT_WORK(&o->deferred_work, br_offload_deferred_work);
++ INIT_WORK(&o->gc_work, br_offload_gc_work);
++}
+
+static inline void br_offload_skb_disable(struct sk_buff *skb)
+{
--
2.34.1
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