Commit 6664498280cf ("packet: call fanout_release, while UNREGISTERING a
netdev"), unfortunately, introduced the following issues.
1. calling mutex_lock(&fanout_mutex) (fanout_release()) from inside
rcu_read-side critical section. rcu_read_lock disables preemption, most often,
which prohibits calling sleeping functions.
[ ] include/linux/rcupdate.h:560 Illegal context switch in RCU read-side
critical section!
[ ]
[ ] rcu_scheduler_active = 1, debug_locks = 0
[ ] 4 locks held by ovs-vswitchd/1969:
[ ] #0: (cb_lock){++++++}, at: [<ffffffff8158a6c9>] genl_rcv+0x19/0x40
[ ] #1: (ovs_mutex){+.+.+.}, at: [<ffffffffa04878ca>]
ovs_vport_cmd_del+0x4a/0x100 [openvswitch]
[ ] #2: (rtnl_mutex){+.+.+.}, at: [<ffffffff81564157>] rtnl_lock+0x17/0x20
[ ] #3: (rcu_read_lock){......}, at: [<ffffffff81614165>]
packet_notifier+0x5/0x3f0
[ ]
[ ] Call Trace:
[ ] [<ffffffff813770c1>] dump_stack+0x85/0xc4
[ ] [<ffffffff810c9077>] lockdep_rcu_suspicious+0x107/0x110
[ ] [<ffffffff810a2da7>] ___might_sleep+0x57/0x210
[ ] [<ffffffff810a2fd0>] __might_sleep+0x70/0x90
[ ] [<ffffffff8162e80c>] mutex_lock_nested+0x3c/0x3a0
[ ] [<ffffffff810de93f>] ? vprintk_default+0x1f/0x30
[ ] [<ffffffff81186e88>] ? printk+0x4d/0x4f
[ ] [<ffffffff816106dd>] fanout_release+0x1d/0xe0
[ ] [<ffffffff81614459>] packet_notifier+0x2f9/0x3f0
2. calling mutex_lock(&fanout_mutex) inside spin_lock(&po->bind_lock).
"sleeping function called from invalid context"
[ ] BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:620
[ ] in_atomic(): 1, irqs_disabled(): 0, pid: 1969, name: ovs-vswitchd
[ ] INFO: lockdep is turned off.
[ ] Call Trace:
[ ] [<ffffffff813770c1>] dump_stack+0x85/0xc4
[ ] [<ffffffff810a2f52>] ___might_sleep+0x202/0x210
[ ] [<ffffffff810a2fd0>] __might_sleep+0x70/0x90
[ ] [<ffffffff8162e80c>] mutex_lock_nested+0x3c/0x3a0
[ ] [<ffffffff816106dd>] fanout_release+0x1d/0xe0
[ ] [<ffffffff81614459>] packet_notifier+0x2f9/0x3f0
3. calling dev_remove_pack(&fanout->prot_hook), from inside
spin_lock(&po->bind_lock) or rcu_read-side critical-section. dev_remove_pack()
-> synchronize_net(), which might sleep.
[ ] BUG: scheduling while atomic: ovs-vswitchd/1969/0x00000002
[ ] INFO: lockdep is turned off.
[ ] Call Trace:
[ ] [<ffffffff813770c1>] dump_stack+0x85/0xc4
[ ] [<ffffffff81186274>] __schedule_bug+0x64/0x73
[ ] [<ffffffff8162b8cb>] __schedule+0x6b/0xd10
[ ] [<ffffffff8162c5db>] schedule+0x6b/0x80
[ ] [<ffffffff81630b1d>] schedule_timeout+0x38d/0x410
[ ] [<ffffffff810ea3fd>] synchronize_sched_expedited+0x53d/0x810
[ ] [<ffffffff810ea6de>] synchronize_rcu_expedited+0xe/0x10
[ ] [<ffffffff8154eab5>] synchronize_net+0x35/0x50
[ ] [<ffffffff8154eae3>] dev_remove_pack+0x13/0x20
[ ] [<ffffffff8161077e>] fanout_release+0xbe/0xe0
[ ] [<ffffffff81614459>] packet_notifier+0x2f9/0x3f0
4. fanout_release() races with calls from different CPU.
To fix the above problems, remove the call to fanout_release() under
rcu_read_lock(). Instead, call __dev_remove_pack(&fanout->prot_hook) and
netdev_run_todo will be happy that &dev->ptype_specific list is empty. In order
to achieve this, I moved dev_{add,remove}_pack() out of fanout_{add,release} to
__fanout_{link,unlink}. So, call to {,__}unregister_prot_hook() will make sure
fanout->prot_hook is removed as well.
Fixes: 6664498280cf ("packet: call fanout_release, while UNREGISTERING a
netdev")
Reported-by: Eric Dumazet <eduma...@google.com>
Signed-off-by: Anoob Soman <anoob.so...@citrix.com>
---
Changes in v3:
- Removed extra variable from fanout_release(), per Eric's suggestion.
Changes in v2:
- Incorporated Eric's suggestion to do fanout_release_data() and kfree() after
synchronize_net()
net/packet/af_packet.c | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 0f03f6a..70f5b6a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1497,6 +1497,8 @@ static void __fanout_link(struct sock *sk, struct
packet_sock *po)
f->arr[f->num_members] = sk;
smp_wmb();
f->num_members++;
+ if (f->num_members == 1)
+ dev_add_pack(&f->prot_hook);
spin_unlock(&f->lock);
}
@@ -1513,6 +1515,8 @@ static void __fanout_unlink(struct sock *sk, struct
packet_sock *po)
BUG_ON(i >= f->num_members);
f->arr[i] = f->arr[f->num_members - 1];
f->num_members--;
+ if (f->num_members == 0)
+ __dev_remove_pack(&f->prot_hook);
spin_unlock(&f->lock);
}
@@ -1693,7 +1697,6 @@ static int fanout_add(struct sock *sk, u16 id, u16
type_flags)
match->prot_hook.func = packet_rcv_fanout;
match->prot_hook.af_packet_priv = match;
match->prot_hook.id_match = match_fanout_group;
- dev_add_pack(&match->prot_hook);
list_add(&match->list, &fanout_list);
}
err = -EINVAL;
@@ -1718,7 +1721,12 @@ static int fanout_add(struct sock *sk, u16 id, u16
type_flags)
return err;
}
-static void fanout_release(struct sock *sk)
+/* If pkt_sk(sk)->fanout->sk_ref is zero, this function removes
+ * pkt_sk(sk)->fanout from fanout_list and returns pkt_sk(sk)->fanout.
+ * It is the responsibility of the caller to call fanout_release_data() and
+ * free the returned packet_fanout (after synchronize_net())
+ */
+static struct packet_fanout *fanout_release(struct sock *sk)
{
struct packet_sock *po = pkt_sk(sk);
struct packet_fanout *f;
@@ -1728,17 +1736,17 @@ static void fanout_release(struct sock *sk)
if (f) {
po->fanout = NULL;
- if (atomic_dec_and_test(&f->sk_ref)) {
+ if (atomic_dec_and_test(&f->sk_ref))
list_del(&f->list);
- dev_remove_pack(&f->prot_hook);
- fanout_release_data(f);
- kfree(f);
- }
+ else
+ f = NULL;
if (po->rollover)
kfree_rcu(po->rollover, rcu);
}
mutex_unlock(&fanout_mutex);
+
+ return f;
}
static bool packet_extra_vlan_len_allowed(const struct net_device *dev,
@@ -2912,6 +2920,7 @@ static int packet_release(struct socket *sock)
{
struct sock *sk = sock->sk;
struct packet_sock *po;
+ struct packet_fanout *f;
struct net *net;
union tpacket_req_u req_u;
@@ -2951,9 +2960,14 @@ static int packet_release(struct socket *sock)
packet_set_ring(sk, &req_u, 1, 1);
}
- fanout_release(sk);
+ f = fanout_release(sk);
synchronize_net();
+
+ if (f) {
+ fanout_release_data(f);
+ kfree(f);
+ }
/*
* Now the socket is dead. No more input will appear.
*/
@@ -3905,7 +3919,6 @@ static int packet_notifier(struct notifier_block *this,
}
if (msg == NETDEV_UNREGISTER) {
packet_cached_dev_reset(po);
- fanout_release(sk);
po->ifindex = -1;
if (po->prot_hook.dev)
dev_put(po->prot_hook.dev);
--
2.7.4
