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    Subject[PATCH 4.4 280/342] target: Fix LUN_RESET active TMR descriptor handling
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Nicholas Bellinger <nab@linux-iscsi.org>

    commit a6d9bb1c9605cd4f44e2d8290dc4d0e88f20292d upstream.

    This patch fixes a NULL pointer se_cmd->cmd_kref < 0
    refcount bug during TMR LUN_RESET with active TMRs,
    triggered during se_cmd + se_tmr_req descriptor
    shutdown + release via core_tmr_drain_tmr_list().

    To address this bug, go ahead and obtain a local
    kref_get_unless_zero(&se_cmd->cmd_kref) for active I/O
    to set CMD_T_ABORTED, and transport_wait_for_tasks()
    followed by the final target_put_sess_cmd() to drop
    the local ->cmd_kref.

    Also add two new checks within target_tmr_work() to
    avoid CMD_T_ABORTED -> TFO->queue_tm_rsp() callbacks
    ahead of invoking the backend -> fabric put in
    transport_cmd_check_stop_to_fabric().

    For good measure, also change core_tmr_release_req()
    to use list_del_init() ahead of se_tmr_req memory
    free.

    Reviewed-by: Quinn Tran <quinn.tran@qlogic.com>
    Cc: Himanshu Madhani <himanshu.madhani@qlogic.com>
    Cc: Sagi Grimberg <sagig@mellanox.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Hannes Reinecke <hare@suse.de>
    Cc: Andy Grover <agrover@redhat.com>
    Cc: Mike Christie <mchristi@redhat.com>
    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/target/target_core_tmr.c | 22 +++++++++++++++++++++-
    drivers/target/target_core_transport.c | 17 +++++++++++++++++
    2 files changed, 38 insertions(+), 1 deletion(-)

    --- a/drivers/target/target_core_tmr.c
    +++ b/drivers/target/target_core_tmr.c
    @@ -68,7 +68,7 @@ void core_tmr_release_req(struct se_tmr_

    if (dev) {
    spin_lock_irqsave(&dev->se_tmr_lock, flags);
    - list_del(&tmr->tmr_list);
    + list_del_init(&tmr->tmr_list);
    spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
    }

    @@ -194,9 +194,11 @@ static void core_tmr_drain_tmr_list(
    struct list_head *preempt_and_abort_list)
    {
    LIST_HEAD(drain_tmr_list);
    + struct se_session *sess;
    struct se_tmr_req *tmr_p, *tmr_pp;
    struct se_cmd *cmd;
    unsigned long flags;
    + bool rc;
    /*
    * Release all pending and outgoing TMRs aside from the received
    * LUN_RESET tmr..
    @@ -222,17 +224,31 @@ static void core_tmr_drain_tmr_list(
    if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
    continue;

    + sess = cmd->se_sess;
    + if (WARN_ON_ONCE(!sess))
    + continue;
    +
    + spin_lock(&sess->sess_cmd_lock);
    spin_lock(&cmd->t_state_lock);
    if (!(cmd->transport_state & CMD_T_ACTIVE)) {
    spin_unlock(&cmd->t_state_lock);
    + spin_unlock(&sess->sess_cmd_lock);
    continue;
    }
    if (cmd->t_state == TRANSPORT_ISTATE_PROCESSING) {
    spin_unlock(&cmd->t_state_lock);
    + spin_unlock(&sess->sess_cmd_lock);
    continue;
    }
    + cmd->transport_state |= CMD_T_ABORTED;
    spin_unlock(&cmd->t_state_lock);

    + rc = kref_get_unless_zero(&cmd->cmd_kref);
    + spin_unlock(&sess->sess_cmd_lock);
    + if (!rc) {
    + printk("LUN_RESET TMR: non-zero kref_get_unless_zero\n");
    + continue;
    + }
    list_move_tail(&tmr_p->tmr_list, &drain_tmr_list);
    }
    spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
    @@ -246,7 +262,11 @@ static void core_tmr_drain_tmr_list(
    (preempt_and_abort_list) ? "Preempt" : "", tmr_p,
    tmr_p->function, tmr_p->response, cmd->t_state);

    + cancel_work_sync(&cmd->work);
    + transport_wait_for_tasks(cmd);
    +
    transport_cmd_finish_abort(cmd, 1);
    + target_put_sess_cmd(cmd);
    }
    }

    --- a/drivers/target/target_core_transport.c
    +++ b/drivers/target/target_core_transport.c
    @@ -2891,8 +2891,17 @@ static void target_tmr_work(struct work_
    struct se_cmd *cmd = container_of(work, struct se_cmd, work);
    struct se_device *dev = cmd->se_dev;
    struct se_tmr_req *tmr = cmd->se_tmr_req;
    + unsigned long flags;
    int ret;

    + spin_lock_irqsave(&cmd->t_state_lock, flags);
    + if (cmd->transport_state & CMD_T_ABORTED) {
    + tmr->response = TMR_FUNCTION_REJECTED;
    + spin_unlock_irqrestore(&cmd->t_state_lock, flags);
    + goto check_stop;
    + }
    + spin_unlock_irqrestore(&cmd->t_state_lock, flags);
    +
    switch (tmr->function) {
    case TMR_ABORT_TASK:
    core_tmr_abort_task(dev, tmr, cmd->se_sess);
    @@ -2925,9 +2934,17 @@ static void target_tmr_work(struct work_
    break;
    }

    + spin_lock_irqsave(&cmd->t_state_lock, flags);
    + if (cmd->transport_state & CMD_T_ABORTED) {
    + spin_unlock_irqrestore(&cmd->t_state_lock, flags);
    + goto check_stop;
    + }
    cmd->t_state = TRANSPORT_ISTATE_PROCESSING;
    + spin_unlock_irqrestore(&cmd->t_state_lock, flags);
    +
    cmd->se_tfo->queue_tm_rsp(cmd);

    +check_stop:
    transport_cmd_check_stop_to_fabric(cmd);
    }
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