From: Hannes Reinecke <hare@suse.de>
Date: Fri, 30 Sep 2016 09:01:15 +0000 (+0200)
Subject: scsi: libfc: Fixup disc_mutex handling
X-Git-Tag: v4.1.12-124.31.3~132
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=6f58c151fbd8fd3152fb3072eef45367963140ef;p=users%2Fjedix%2Flinux-maple.git

scsi: libfc: Fixup disc_mutex handling

The list of attached 'rdata' remote port structures is RCU
protected, so there is no need to take the 'disc_mutex' when
traversing it.
Rather we should be using rcu_read_lock() and kref_get_unless_zero()
to validate the entries.
We need, however, take the disc_mutex when deleting an entry;
otherwise we risk clashes with list_add.

Orabug: 25933179

Reviewed-by: John Sobecki <john.sobecki@oracle.com>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Acked-by: Johannes Thumshirn <jth@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Rajan Shanmugavelu <rajan.shanmugavelu@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/drivers/scsi/libfc/fc_rport.c b/drivers/scsi/libfc/fc_rport.c
index 4ec896e42120..a0ceba10c679 100644
--- a/drivers/scsi/libfc/fc_rport.c
+++ b/drivers/scsi/libfc/fc_rport.c
@@ -378,7 +378,9 @@ static void fc_rport_work(struct work_struct *work)
 				mutex_unlock(&rdata->rp_mutex);
 			} else {
 				FC_RPORT_DBG(rdata, "work delete\n");
+				mutex_lock(&lport->disc.disc_mutex);
 				list_del_rcu(&rdata->peers);
+				mutex_unlock(&lport->disc.disc_mutex);
 				mutex_unlock(&rdata->rp_mutex);
 				kref_put(&rdata->kref, lport->tt.rport_destroy);
 			}