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    Subject[PATCH 4.9 53/65] s390/qeth: fix double-free on IP add/remove race
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Julian Wiedmann <jwi@linux.vnet.ibm.com>


    [ Upstream commit 14d066c3531a87f727968cacd85bd95c75f59843 ]

    Registering an IPv4 address with the HW takes quite a while, so we
    temporarily drop the ip_htable lock. Any concurrent add/remove of the
    same IP adjusts the IP's use count, and (on remove) is then blocked by
    addr->in_progress.
    After the register call has completed, we check the use count for
    concurrently attempted add/remove calls - and possibly straight-away
    deregister the IP again. This happens via l3_delete_ip(), which
    1) looks up the queried IP in the htable (getting a reference to the
    *same* queried object),
    2) deregisters the IP from the HW, and
    3) frees the IP object.

    The caller in l3_add_ip() then does a second free on the same object.

    For this case, skip all the extra checks and lookups in l3_delete_ip()
    and just deregister & free the IP object ourselves.

    Fixes: 5f78e29ceebf ("qeth: optimize IP handling in rx_mode callback")
    Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/s390/net/qeth_l3_main.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/drivers/s390/net/qeth_l3_main.c
    +++ b/drivers/s390/net/qeth_l3_main.c
    @@ -323,7 +323,8 @@ int qeth_l3_add_ip(struct qeth_card *car
    (rc == IPA_RC_LAN_OFFLINE)) {
    addr->disp_flag = QETH_DISP_ADDR_DO_NOTHING;
    if (addr->ref_counter < 1) {
    - qeth_l3_delete_ip(card, addr);
    + qeth_l3_deregister_addr_entry(card, addr);
    + hash_del(&addr->hnode);
    kfree(addr);
    }
    } else {

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