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    Subject[patch 09/18] IB/mad: Fix race between cancel and receive completion
    -stable review patch.  If anyone has any objections, please let us know.

    From: Roland Dreier <>

    When ib_cancel_mad() is called, it puts the canceled send on a list
    and schedules a "flushed" callback from process context. However,
    this leaves a window where a receive completion could be processed
    before the send is fully flushed.

    This is fine, except that ib_find_send_mad() will find the MAD and
    return it to the receive processing, which results in the sender
    getting both a successful receive and a "flushed" send completion for
    the same request. Understandably, this confuses the sender, which is
    expecting only one of these two callbacks, and leads to grief such as
    a use-after-free in IPoIB.

    Fix this by changing ib_find_send_mad() to return a send struct only
    if the status is still successful (and not "flushed"). The search of
    the send_list already had this check, so this patch just adds the same
    check to the search of the wait_list.

    Signed-off-by: Roland Dreier <>
    Signed-off-by: Chris Wright <>
    Signed-off-by: Greg Kroah-Hartman <>

    drivers/infiniband/core/mad.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- linux-
    +++ linux-
    @@ -1750,7 +1750,7 @@ ib_find_send_mad(struct ib_mad_agent_pri
    (is_direct(wc->recv_buf.mad->mad_hdr.mgmt_class) ||
    rcv_has_same_gid(mad_agent_priv, wr, wc)))
    - return wr;
    + return (wr->status == IB_WC_SUCCESS) ? wr : NULL;

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