[PATCH AUTOSEL 5.3 56/71] macsec: drop skb sk before calling gro_cells_receive

Sasha Levin
2019-10-01T16:41:01Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit ba56d8ce38c8252fff5b745db3899cf092578ede ]

Fei Liu reported a crash when doing netperf on a topo of macsec
dev over veth:

[ 448.919128] refcount_t: underflow; use-after-free.
[ 449.090460] Call trace:
[ 449.092895] refcount_sub_and_test+0xb4/0xc0
[ 449.097155] tcp_wfree+0x2c/0x150
[ 449.100460] ip_rcv+0x1d4/0x3a8
[ 449.103591] __netif_receive_skb_core+0x554/0xae0
[ 449.108282] __netif_receive_skb+0x28/0x78
[ 449.112366] netif_receive_skb_internal+0x54/0x100
[ 449.117144] napi_gro_complete+0x70/0xc0
[ 449.121054] napi_gro_flush+0x6c/0x90
[ 449.124703] napi_complete_done+0x50/0x130
[ 449.128788] gro_cell_poll+0x8c/0xa8
[ 449.132351] net_rx_action+0x16c/0x3f8
[ 449.136088] __do_softirq+0x128/0x320

The issue was caused by skb's true_size changed without its sk's
sk_wmem_alloc increased in tcp/skb_gro_receive(). Later when the
skb is being freed and the skb's truesize is subtracted from its
sk's sk_wmem_alloc in tcp_wfree(), underflow occurs.

macsec is calling gro_cells_receive() to receive a packet, which
actually requires skb->sk to be NULL. However when macsec dev is
over veth, it's possible the skb->sk is still set if the skb was
not unshared or expanded from the peer veth.

ip_rcv() is calling skb_orphan() to drop the skb's sk for tproxy,
but it is too late for macsec's calling gro_cells_receive(). So
fix it by dropping the skb's sk earlier on rx path of macsec.

Fixes: 5491e7c6b1a9 ("macsec: enable GRO and RPS on macsec devices")
Reported-by: Xiumei Mu <xmu@redhat.com>
Reported-by: Fei Liu <feliu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/macsec.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 8f46aa1ddec01..cb7637364b40d 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -1235,6 +1235,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
macsec_rxsa_put(rx_sa);
macsec_rxsc_put(rx_sc);

+ skb_orphan(skb);
ret = gro_cells_receive(&macsec->gro_cells, skb);
if (ret == NET_RX_SUCCESS)
count_rx(dev, skb->len);
--
2.20.1