| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 059/105] packet: hold bind lock when rebinding to fanout hook | Date | Tue, 10 Oct 2017 21:50:30 +0200 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Willem de Bruijn <willemb@google.com>
[ Upstream commit 008ba2a13f2d04c947adc536d19debb8fe66f110 ]
Packet socket bind operations must hold the po->bind_lock. This keeps po->running consistent with whether the socket is actually on a ptype list to receive packets.
fanout_add unbinds a socket and its packet_rcv/tpacket_rcv call, then binds the fanout object to receive through packet_rcv_fanout.
Make it hold the po->bind_lock when testing po->running and rebinding. Else, it can race with other rebind operations, such as that in packet_set_ring from packet_rcv to tpacket_rcv. Concurrent updates can result in a socket being added to a fanout group twice, causing use-after-free KASAN bug reports, among others.
Reported independently by both trinity and syzkaller. Verified that the syzkaller reproducer passes after this patch.
Fixes: dc99f600698d ("packet: Add fanout support.") Reported-by: nixioaming <nixiaoming@huawei.com> Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/packet/af_packet.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
--- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1648,10 +1648,6 @@ static int fanout_add(struct sock *sk, u mutex_lock(&fanout_mutex); - err = -EINVAL; - if (!po->running) - goto out; - err = -EALREADY; if (po->fanout) goto out; @@ -1700,7 +1696,10 @@ static int fanout_add(struct sock *sk, u list_add(&match->list, &fanout_list); } err = -EINVAL; - if (match->type == type && + + spin_lock(&po->bind_lock); + if (po->running && + match->type == type && match->prot_hook.type == po->prot_hook.type && match->prot_hook.dev == po->prot_hook.dev) { err = -ENOSPC; @@ -1712,6 +1711,13 @@ static int fanout_add(struct sock *sk, u err = 0; } } + spin_unlock(&po->bind_lock); + + if (err && !refcount_read(&match->sk_ref)) { + list_del(&match->list); + kfree(match); + } + out: if (err && rollover) { kfree(rollover);
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