packet: Do not call fanout_release from atomic contexts

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 <edumazet@google.com>
Signed-off-by: Anoob Soman <anoob.soman@citrix.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 0f03f6a53b4ddb8093a2122914200c0738af8fb3..70f5b6a4683c29351284e3385f56caf1bce37ac7 100644 (file)
--- 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 @@ 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);