Commit d199fab6 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

packet: fix races in fanout_add() 



Multiple threads can call fanout_add() at the same time.

We need to grab fanout_mutex earlier to avoid races that could
lead to one thread freeing po->rollover that was set by another thread.

Do the same in fanout_release(), for peace of mind, and to help us
finding lockdep issues earlier.

Fixes: dc99f600 ("packet: Add fanout support.")
Fixes: 0648ab70 ("packet: rollover prepare: per-socket state")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f39f0d1e

net/packet/af_packet.c

+30 −25
Original line number Diff line number Diff line
@@ -1619,6 +1619,7 @@ static void fanout_release_data(struct packet_fanout *f) 


static int fanout_add(struct sock *sk, u16 id, u16 type_flags)

{

	struct packet_rollover *rollover = NULL;

	struct packet_sock *po = pkt_sk(sk);

	struct packet_fanout *f, *match;

	u8 type = type_flags & 0xff;
@@ -1641,23 +1642,28 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) 
		return -EINVAL;

	}



	mutex_lock(&fanout_mutex);



	err = -EINVAL;

	if (!po->running)

		return -EINVAL;

		goto out;



	err = -EALREADY;

	if (po->fanout)

		return -EALREADY;

		goto out;



	if (type == PACKET_FANOUT_ROLLOVER ||

	    (type_flags & PACKET_FANOUT_FLAG_ROLLOVER)) {

		po->rollover = kzalloc(sizeof(*po->rollover), GFP_KERNEL);

		if (!po->rollover)

			return -ENOMEM;

		atomic_long_set(&po->rollover->num, 0);

		atomic_long_set(&po->rollover->num_huge, 0);

		atomic_long_set(&po->rollover->num_failed, 0);

		err = -ENOMEM;

		rollover = kzalloc(sizeof(*rollover), GFP_KERNEL);

		if (!rollover)

			goto out;

		atomic_long_set(&rollover->num, 0);

		atomic_long_set(&rollover->num_huge, 0);

		atomic_long_set(&rollover->num_failed, 0);

		po->rollover = rollover;

	}



	mutex_lock(&fanout_mutex);

	match = NULL;

	list_for_each_entry(f, &fanout_list, list) {

		if (f->id == id &&
@@ -1704,11 +1710,11 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) 
		}

	}

out:

	mutex_unlock(&fanout_mutex);

	if (err) {

		kfree(po->rollover);

	if (err && rollover) {

		kfree(rollover);

		po->rollover = NULL;

	}

	mutex_unlock(&fanout_mutex);

	return err;

}
@@ -1717,11 +1723,9 @@ static void fanout_release(struct sock *sk) 
	struct packet_sock *po = pkt_sk(sk);

	struct packet_fanout *f;



	f = po->fanout;

	if (!f)

		return;



	mutex_lock(&fanout_mutex);

	f = po->fanout;

	if (f) {

		po->fanout = NULL;



		if (atomic_dec_and_test(&f->sk_ref)) {
@@ -1730,11 +1734,12 @@ static void fanout_release(struct sock *sk) 
			fanout_release_data(f);

			kfree(f);

		}

	mutex_unlock(&fanout_mutex);



		if (po->rollover)

			kfree_rcu(po->rollover, rcu);

	}

	mutex_unlock(&fanout_mutex);

}



static bool packet_extra_vlan_len_allowed(const struct net_device *dev,

					  struct sk_buff *skb)

CRA Git | Maintained and supported by SUSTech CRA and CCSE