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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: dc99f60069 ("packet: Add fanout support.")
Fixes: 0648ab70af ("packet: rollover prepare: per-socket state")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2017-02-14 09:03:51 -08:00 committed by David S. Miller
parent f39f0d1e1e
commit d199fab63c
1 changed files with 31 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
net/packet/af_packet.c
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@ -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;
}
if (!po->running)
return -EINVAL;
mutex_lock(&fanout_mutex);
err = -EINVAL;
if (!po->running)
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;
}
@ -1717,23 +1723,22 @@ 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);
po->fanout = NULL;
f = po->fanout;
if (f) {
po->fanout = NULL;
if (atomic_dec_and_test(&f->sk_ref)) {
list_del(&f->list);
dev_remove_pack(&f->prot_hook);
fanout_release_data(f);
kfree(f);
if (atomic_dec_and_test(&f->sk_ref)) {
list_del(&f->list);
dev_remove_pack(&f->prot_hook);
fanout_release_data(f);
kfree(f);
}
if (po->rollover)
kfree_rcu(po->rollover, rcu);
}
mutex_unlock(&fanout_mutex);
if (po->rollover)
kfree_rcu(po->rollover, rcu);
}
static bool packet_extra_vlan_len_allowed(const struct net_device *dev,