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authorPavel Emelyanov <xemul@parallels.com>2012-08-21 01:06:47 +0000
committerDavid S. Miller <davem@davemloft.net>2012-08-22 22:58:27 -0700
commit0fa7fa98dbcc2789409ed24e885485e645803d7f (patch)
tree30a9b851fdee3b01a64f5ee07940224d089d31de /net/packet/diag.c
parentb32607dd47d456b99f0a16f1c37bc8a0975ffb19 (diff)
downloadlinux-0fa7fa98dbcc2789409ed24e885485e645803d7f.tar.gz
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/diag.c')
-rw-r--r--net/packet/diag.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/net/packet/diag.c b/net/packet/diag.c
index bc33fbe8a5e..39bce0d50df 100644
--- a/net/packet/diag.c
+++ b/net/packet/diag.c
@@ -177,8 +177,8 @@ static int packet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
net = sock_net(skb->sk);
req = nlmsg_data(cb->nlh);
- rcu_read_lock();
- sk_for_each_rcu(sk, node, &net->packet.sklist) {
+ mutex_lock(&net->packet.sklist_lock);
+ sk_for_each(sk, node, &net->packet.sklist) {
if (!net_eq(sock_net(sk), net))
continue;
if (num < s_num)
@@ -192,7 +192,7 @@ next:
num++;
}
done:
- rcu_read_unlock();
+ mutex_unlock(&net->packet.sklist_lock);
cb->args[0] = num;
return skb->len;