Commit b8273570 authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
Browse files

genetlink: fix netns vs. netlink table locking (2) 



Similar to commit d136f1bd,
there's a bug when unregistering a generic netlink family,
which is caught by the might_sleep() added in that commit:

    BUG: sleeping function called from invalid context at net/netlink/af_netlink.c:183
    in_atomic(): 1, irqs_disabled(): 0, pid: 1510, name: rmmod
    2 locks held by rmmod/1510:
     #0:  (genl_mutex){+.+.+.}, at: [<ffffffff8138283b>] genl_unregister_family+0x2b/0x130
     #1:  (rcu_read_lock){.+.+..}, at: [<ffffffff8138270c>] __genl_unregister_mc_group+0x1c/0x120
    Pid: 1510, comm: rmmod Not tainted 2.6.31-wl #444
    Call Trace:
     [<ffffffff81044ff9>] __might_sleep+0x119/0x150
     [<ffffffff81380501>] netlink_table_grab+0x21/0x100
     [<ffffffff813813a3>] netlink_clear_multicast_users+0x23/0x60
     [<ffffffff81382761>] __genl_unregister_mc_group+0x71/0x120
     [<ffffffff81382866>] genl_unregister_family+0x56/0x130
     [<ffffffffa0007d85>] nl80211_exit+0x15/0x20 [cfg80211]
     [<ffffffffa000005a>] cfg80211_exit+0x1a/0x40 [cfg80211]

Fix in the same way by grabbing the netlink table lock
before doing rcu_read_lock().

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 704cc92e

include/linux/netlink.h

+1 −0
Original line number Diff line number Diff line
@@ -187,6 +187,7 @@ extern struct sock *netlink_kernel_create(struct net *net, 
extern void netlink_kernel_release(struct sock *sk);

extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);

extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);

extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);

extern void netlink_clear_multicast_users(struct sock *sk, unsigned int group);

extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);

extern int netlink_has_listeners(struct sock *sk, unsigned int group);

net/netlink/af_netlink.c

+11 −8
Original line number Diff line number Diff line
@@ -1609,6 +1609,16 @@ int netlink_change_ngroups(struct sock *sk, unsigned int groups) 
	return err;

}



void __netlink_clear_multicast_users(struct sock *ksk, unsigned int group)

{

	struct sock *sk;

	struct hlist_node *node;

	struct netlink_table *tbl = &nl_table[ksk->sk_protocol];



	sk_for_each_bound(sk, node, &tbl->mc_list)

		netlink_update_socket_mc(nlk_sk(sk), group, 0);

}



/**

 * netlink_clear_multicast_users - kick off multicast listeners

 *
@@ -1619,15 +1629,8 @@ int netlink_change_ngroups(struct sock *sk, unsigned int groups) 
 */

void netlink_clear_multicast_users(struct sock *ksk, unsigned int group)

{

	struct sock *sk;

	struct hlist_node *node;

	struct netlink_table *tbl = &nl_table[ksk->sk_protocol];



	netlink_table_grab();



	sk_for_each_bound(sk, node, &tbl->mc_list)

		netlink_update_socket_mc(nlk_sk(sk), group, 0);



	__netlink_clear_multicast_users(ksk, group);

	netlink_table_ungrab();

}

net/netlink/genetlink.c

+3 −1
Original line number Diff line number Diff line
@@ -220,10 +220,12 @@ static void __genl_unregister_mc_group(struct genl_family *family, 
	struct net *net;

	BUG_ON(grp->family != family);



	netlink_table_grab();

	rcu_read_lock();

	for_each_net_rcu(net)

		netlink_clear_multicast_users(net->genl_sock, grp->id);

		__netlink_clear_multicast_users(net->genl_sock, grp->id);

	rcu_read_unlock();

	netlink_table_ungrab();



	clear_bit(grp->id, mc_groups);

	list_del(&grp->list);

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