diff options
| author | Pavel Emelyanov <xemul@parallels.com> | 2012-08-21 01:06:47 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-08-22 22:58:27 -0700 |
| commit | 0fa7fa98dbcc2789409ed24e885485e645803d7f (patch) | |
| tree | 30a9b851fdee3b01a64f5ee07940224d089d31de /net/packet/af_packet.c | |
| parent | b32607dd47d456b99f0a16f1c37bc8a0975ffb19 (diff) | |
packet: Protect packet sk list with mutex (v2)
Change since v1:
* Fixed inuse counters access spotted by Eric
In patch eea68e2f (packet: Report socket mclist info via diag module) I've
introduced a "scheduling in atomic" problem in packet diag module -- the
socket list is traversed under rcu_read_lock() while performed under it sk
mclist access requires rtnl lock (i.e. -- mutex) to be taken.
[152363.820563] BUG: scheduling while atomic: crtools/12517/0x10000002
[152363.820573] 4 locks held by crtools/12517:
[152363.820581] #0: (sock_diag_mutex){+.+.+.}, at: [<ffffffff81a2dcb5>] sock_diag_rcv+0x1f/0x3e
[152363.820613] #1: (sock_diag_table_mutex){+.+.+.}, at: [<ffffffff81a2de70>] sock_diag_rcv_msg+0xdb/0x11a
[152363.820644] #2: (nlk->cb_mutex){+.+.+.}, at: [<ffffffff81a67d01>] netlink_dump+0x23/0x1ab
[152363.820693] #3: (rcu_read_lock){.+.+..}, at: [<ffffffff81b6a049>] packet_diag_dump+0x0/0x1af
Similar thing was then re-introduced by further packet diag patches (fanount
mutex and pgvec mutex for rings) :(
Apart from being terribly sorry for the above, I propose to change the packet
sk list protection from spinlock to mutex. This lock currently protects two
modifications:
* sklist
* prot inuse counters
The sklist modifications can be just reprotected with mutex since they already
occur in a sleeping context. The inuse counters modifications are trickier -- the
__this_cpu_-s are used inside, thus requiring the caller to handle the potential
issues with contexts himself. Since packet sockets' counters are modified in two
places only (packet_create and packet_release) we only need to protect the context
from being preempted. BH disabling is not required in this case.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/packet/af_packet.c')
| -rw-r--r-- | net/packet/af_packet.c | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index bfaa0a83f0e..f220c5bdb71 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2317,10 +2317,13 @@ static int packet_release(struct socket *sock) net = sock_net(sk); po = pkt_sk(sk); - spin_lock_bh(&net->packet.sklist_lock); + mutex_lock(&net->packet.sklist_lock); sk_del_node_init_rcu(sk); + mutex_unlock(&net->packet.sklist_lock); + + preempt_disable(); sock_prot_inuse_add(net, sk->sk_prot, -1); - spin_unlock_bh(&net->packet.sklist_lock); + preempt_enable(); spin_lock(&po->bind_lock); unregister_prot_hook(sk, false); @@ -2519,10 +2522,13 @@ static int packet_create(struct net *net, struct socket *sock, int protocol, register_prot_hook(sk); } - spin_lock_bh(&net->packet.sklist_lock); + mutex_lock(&net->packet.sklist_lock); sk_add_node_rcu(sk, &net->packet.sklist); + mutex_unlock(&net->packet.sklist_lock); + + preempt_disable(); sock_prot_inuse_add(net, &packet_proto, 1); - spin_unlock_bh(&net->packet.sklist_lock); + preempt_enable(); return 0; out: @@ -3775,7 +3781,7 @@ static const struct file_operations packet_seq_fops = { static int __net_init packet_net_init(struct net *net) { - spin_lock_init(&net->packet.sklist_lock); + mutex_init(&net->packet.sklist_lock); INIT_HLIST_HEAD(&net->packet.sklist); if (!proc_net_fops_create(net, "packet", 0, &packet_seq_fops)) |