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    Subject[PATCH 4.9 025/129] macsec: drop skb sk before calling gro_cells_receive
    Date
    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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/macsec.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/drivers/net/macsec.c
    +++ b/drivers/net/macsec.c
    @@ -1240,6 +1240,7 @@ deliver:
    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);

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