Commit 2bd624b4 authored by Anoob Soman's avatar Anoob Soman Committed by David S. Miller
Browse files

packet: Do not call fanout_release from atomic contexts

Commit 66644982 ("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: 66644982

 ("packet: call fanout_release, while UNREGISTERING a netdev")
Reported-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarAnoob Soman <anoob.soman@citrix.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4695daef
......@@ -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 @@ out:
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);
......
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