From d199fab63c11998a602205f7ee7ff7c05c97164b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 14 Feb 2017 09:03:51 -0800 Subject: [PATCH] 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: dc99f600698d ("packet: Add fanout support.") Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller --- net/packet/af_packet.c | 55 +++++++++++++++++++++++------------------- 1 file changed, 30 insertions(+), 25 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index d56ee46b11fc..0f03f6a53b4d 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -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; } @@ -1717,23 +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, -- 2.20.1