packet: hold bind lock when rebinding to fanout hook

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commit 008ba2a13f upstream.

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: dc99f60069 ("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>
[bwh: Backported to 3.16: use atomic_read() not refcount_read()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

...

This commit is contained in:

Willem de Bruijn 2017-09-14 17:14:41 -04:00 • committed by Ben Hutchings

parent 24832178de

commit 4839233c04

1 changed files with 11 additions and 5 deletions

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net/packet/af_packet.c

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