From d136f1bd366fdb7e747ca7e0218171e7a00a98a5 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Sat, 12 Sep 2009 03:03:15 +0000 Subject: genetlink: fix netns vs. netlink table locking Since my commits introducing netns awareness into genetlink we can get this problem: BUG: scheduling while atomic: modprobe/1178/0x00000002 2 locks held by modprobe/1178: #0: (genl_mutex){+.+.+.}, at: [] genl_register_mc_grou #1: (rcu_read_lock){.+.+..}, at: [] genl_register_mc_g Pid: 1178, comm: modprobe Not tainted 2.6.31-rc8-wl-34789-g95cb731-dirty # Call Trace: [] __schedule_bug+0x85/0x90 [] schedule+0x108/0x588 [] netlink_table_grab+0xa1/0xf0 [] netlink_change_ngroups+0x47/0x100 [] genl_register_mc_group+0x12f/0x290 because I overlooked that netlink_table_grab() will schedule, thinking it was just the rwlock. However, in the contention case, that isn't actually true. Fix this by letting the code grab the netlink table lock first and then the RCU for netns protection. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller --- net/netlink/genetlink.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'net/netlink/genetlink.c') diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c index 66f6ba0bab11..566941e03363 100644 --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -176,9 +176,10 @@ int genl_register_mc_group(struct genl_family *family, if (family->netnsok) { struct net *net; + netlink_table_grab(); rcu_read_lock(); for_each_net_rcu(net) { - err = netlink_change_ngroups(net->genl_sock, + err = __netlink_change_ngroups(net->genl_sock, mc_groups_longs * BITS_PER_LONG); if (err) { /* @@ -188,10 +189,12 @@ int genl_register_mc_group(struct genl_family *family, * increased on some sockets which is ok. */ rcu_read_unlock(); + netlink_table_ungrab(); goto out; } } rcu_read_unlock(); + netlink_table_ungrab(); } else { err = netlink_change_ngroups(init_net.genl_sock, mc_groups_longs * BITS_PER_LONG); -- cgit v1.2.3