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packet: fix races in fanout_add() 

commit d199fab63c11998a602205f7ee7ff7c05c97164b upstream.

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: 0648ab70afe6 ("packet: rollover prepare: per-socket state")
Change-Id: I700897ebddd090754635d2f45f8010a2ea35bb07
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2:
 - No rollover queue stats
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Eric Dumazet 2017-02-14 09:03:51 -08:00 committed by LuK1337
parent 94fcbc021a
commit 947bfe2bcc
1 changed files with 17 additions and 15 deletions
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32
net/packet/af_packet.c
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@ -1304,13 +1304,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
return -EINVAL;
}
if (!po->running)
return -EINVAL;
if (po->fanout)
return -EALREADY;
mutex_lock(&fanout_mutex);
err = -EINVAL;
if (!po->running)
goto out;
err = -EALREADY;
if (po->fanout)
goto out;
match = NULL;
list_for_each_entry(f, &fanout_list, list) {
if (f->id == id &&
@ -1366,17 +1369,16 @@ 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);
kfree(f);
if (atomic_dec_and_test(&f->sk_ref)) {
list_del(&f->list);
dev_remove_pack(&f->prot_hook);
kfree(f);
}
}
mutex_unlock(&fanout_mutex);
}