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    Subject[PATCH 4.9 103/125] target: Fix COMPARE_AND_WRITE caw_sem leak during se_cmd quiesce
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Jiang Yi <jiangyilism@gmail.com>

    commit 1d6ef276594a781686058802996e09c8550fd767 upstream.

    This patch addresses a COMPARE_AND_WRITE se_device->caw_sem leak,
    that would be triggered during normal se_cmd shutdown or abort
    via __transport_wait_for_tasks().

    This would occur because target_complete_cmd() would catch this
    early and do complete_all(&cmd->t_transport_stop_comp), but since
    target_complete_ok_work() or target_complete_failure_work() are
    never called to invoke se_cmd->transport_complete_callback(),
    the COMPARE_AND_WRITE specific callbacks never release caw_sem.

    To address this special case, go ahead and release caw_sem
    directly from target_complete_cmd().

    (Remove '&& success' from check, to release caw_sem regardless
    of scsi_status - nab)

    Signed-off-by: Jiang Yi <jiangyilism@gmail.com>
    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/target/target_core_transport.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    --- a/drivers/target/target_core_transport.c
    +++ b/drivers/target/target_core_transport.c
    @@ -753,6 +753,15 @@ void target_complete_cmd(struct se_cmd *
    if (cmd->transport_state & CMD_T_ABORTED ||
    cmd->transport_state & CMD_T_STOP) {
    spin_unlock_irqrestore(&cmd->t_state_lock, flags);
    + /*
    + * If COMPARE_AND_WRITE was stopped by __transport_wait_for_tasks(),
    + * release se_device->caw_sem obtained by sbc_compare_and_write()
    + * since target_complete_ok_work() or target_complete_failure_work()
    + * won't be called to invoke the normal CAW completion callbacks.
    + */
    + if (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) {
    + up(&dev->caw_sem);
    + }
    complete_all(&cmd->t_transport_stop_comp);
    return;
    } else if (!success) {

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