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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jens Remus <jremus@linux.ibm.com>,
        Benjamin Block <bblock@linux.ibm.com>,
        Steffen Maier <maier@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: [PATCH 4.4 040/100] scsi: zfcp: fix missing erp_lock in port recovery trigger for point-to-point
Date:   Wed, 22 Apr 2020 11:56:10 +0200
Message-Id: <20200422095029.732406211@linuxfoundation.org>
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From: Steffen Maier <maier@linux.ibm.com>

commit 819732be9fea728623e1ed84eba28def7384ad1f upstream.

v2.6.27 commit cc8c282963bd ("[SCSI] zfcp: Automatically attach remote
ports") introduced zfcp automatic port scan.

Before that, the user had to use the sysfs attribute "port_add" of an FCP
device (adapter) to add and open remote (target) ports, even for the remote
peer port in point-to-point topology. That code path did a proper port open
recovery trigger taking the erp_lock.

Since above commit, a new helper function zfcp_erp_open_ptp_port()
performed an UNlocked port open recovery trigger. This can race with other
parallel recovery triggers. In zfcp_erp_action_enqueue() this could corrupt
e.g. adapter->erp_total_count or adapter->erp_ready_head.

As already found for fabric topology in v4.17 commit fa89adba1941 ("scsi:
zfcp: fix infinite iteration on ERP ready list"), there was an endless loop
during tracing of rport (un)block.  A subsequent v4.18 commit 9e156c54ace3
("scsi: zfcp: assert that the ERP lock is held when tracing a recovery
trigger") introduced a lockdep assertion for that case.

As a side effect, that lockdep assertion now uncovered the unlocked code
path for PtP. It is from within an adapter ERP action:

zfcp_erp_strategy[1479]  intentionally DROPs erp lock around
                         zfcp_erp_strategy_do_action()
zfcp_erp_strategy_do_action[1441]      NO erp lock
zfcp_erp_adapter_strategy[876]         NO erp lock
zfcp_erp_adapter_strategy_open[855]    NO erp lock
zfcp_erp_adapter_strategy_open_fsf[806]NO erp lock
zfcp_erp_adapter_strat_fsf_xconf[772]  erp lock only around
                                       zfcp_erp_action_to_running(),
                                       BUT *_not_* around
                                       zfcp_erp_enqueue_ptp_port()
zfcp_erp_enqueue_ptp_port[728]         BUG: *_not_* taking erp lock
_zfcp_erp_port_reopen[432]             assumes to be called with erp lock
zfcp_erp_action_enqueue[314]           assumes to be called with erp lock
zfcp_dbf_rec_trig[288]                 _checks_ to be called with erp lock:
	lockdep_assert_held(&adapter->erp_lock);

It causes the following lockdep warning:

WARNING: CPU: 2 PID: 775 at drivers/s390/scsi/zfcp_dbf.c:288
                            zfcp_dbf_rec_trig+0x16a/0x188
no locks held by zfcperp0.0.17c0/775.

Fix this by using the proper locked recovery trigger helper function.

Link: https://lore.kernel.org/r/20200312174505.51294-2-maier@linux.ibm.com
Fixes: cc8c282963bd ("[SCSI] zfcp: Automatically attach remote ports")
Cc: <stable@vger.kernel.org> #v2.6.27+
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/s390/scsi/zfcp_erp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -747,7 +747,7 @@ static void zfcp_erp_enqueue_ptp_port(st
 				 adapter->peer_d_id);
 	if (IS_ERR(port)) /* error or port already attached */
 		return;
-	_zfcp_erp_port_reopen(port, 0, "ereptp1");
+	zfcp_erp_port_reopen(port, 0, "ereptp1");
 }
 
 static int zfcp_erp_adapter_strat_fsf_xconf(struct zfcp_erp_action *erp_action)