scsi: target: core: Remove from tmr_list during LUN unlink

Currently TMF commands are removed from de_device.dev_tmf_list at the very
end of se_cmd lifecycle. However, se_lun unlinks from se_cmd upon a command
status (response) being queued in transport layer. This means that LUN and
backend device can be deleted in the meantime and a panic will occur:

target_tmr_work()
	cmd->se_tfo->queue_tm_rsp(cmd); // send abort_rsp to a wire
	transport_lun_remove_cmd(cmd) // unlink se_cmd from se_lun
- // - // - // -
<<<--- lun remove
<<<--- core backend device remove
- // - // - // -
qlt_handle_abts_completion()
  tfo->free_mcmd()
    transport_generic_free_cmd()
      target_put_sess_cmd()
        core_tmr_release_req() {
          if (dev) { // backend device, can not be null
            spin_lock_irqsave(&dev->se_tmr_lock, flags); //<<<--- CRASH

Call Trace:
NIP [c000000000e1683c] _raw_spin_lock_irqsave+0x2c/0xc0
LR [c00800000e433338] core_tmr_release_req+0x40/0xa0 [target_core_mod]
Call Trace:
(unreliable)
0x0
target_put_sess_cmd+0x2a0/0x370 [target_core_mod]
transport_generic_free_cmd+0x6c/0x1b0 [target_core_mod]
tcm_qla2xxx_complete_mcmd+0x28/0x50 [tcm_qla2xxx]
process_one_work+0x2c4/0x5c0
worker_thread+0x88/0x690

For the iSCSI protocol this is easily reproduced:

 - Send some SCSI sommand

 - Send Abort of that command over iSCSI

 - Remove LUN on target

 - Send next iSCSI command to acknowledge the Abort_Response

 - Target panics

There is no need to keep the command in tmr_list until response completion,
so move the removal from tmr_list from the response completion to the
response queueing when the LUN is unlinked.  Move the removal from state
list too as it is a subject to the same race condition.

Link: https://lore.kernel.org/r/20211018135753.15297-1-d.bogdanov@yadro.com
Fixes: c66ac9db8d4a ("[SCSI] target: Add LIO target core v4.0.0-rc6")
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 1 insertions, 16 deletions

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index e7fcbc09f9db..bac111456fa1 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -50,15 +50,6 @@ EXPORT_SYMBOL(core_tmr_alloc_req);
 
 void core_tmr_release_req(struct se_tmr_req *tmr)
 {
-	struct se_device *dev = tmr->tmr_dev;
-	unsigned long flags;
-
-	if (dev) {
-		spin_lock_irqsave(&dev->se_tmr_lock, flags);
-		list_del_init(&tmr->tmr_list);
-		spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
-	}
-
 	kfree(tmr);
 }
 
@@ -156,13 +147,6 @@ void core_tmr_abort_task(
 			se_cmd->state_active = false;
 			spin_unlock_irqrestore(&dev->queues[i].lock, flags);
 
-			/*
-			 * Ensure that this ABORT request is visible to the LU
-			 * RESET code.
-			 */
-			if (!tmr->tmr_dev)
-				WARN_ON_ONCE(transport_lookup_tmr_lun(tmr->task_cmd) < 0);
-
 			if (dev->transport->tmr_notify)
 				dev->transport->tmr_notify(dev, TMR_ABORT_TASK,
 							   &aborted_list);
@@ -234,6 +218,7 @@ static void core_tmr_drain_tmr_list(
 		}
 
 		list_move_tail(&tmr_p->tmr_list, &drain_tmr_list);
+		tmr_p->tmr_dev = NULL;
 	}
 	spin_unlock_irqrestore(&dev->se_tmr_lock, flags);