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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, Hannes Reinecke <hare@suse.com>,
        Johannes Thumshirn <jth@kernel.org>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 214/235] scsi: libfc: fixup sleeping function called from invalid context
Date:   Mon, 24 Sep 2018 13:53:20 +0200
Message-Id: <20180924113125.046973604@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Hannes Reinecke <hare@suse.de>

[ Upstream commit fa519f701d27198a2858bb108fc18ea9d8c106a7 ]

fc_rport_login() will be calling mutex_lock() while running inside an
RCU-protected section, triggering the warning 'sleeping function called
from invalid context'.  To fix this we can drop the rcu functions here
altogether as the disc mutex protecting the list itself is already held,
preventing any list manipulation.

Fixes: a407c593398c ("scsi: libfc: Fixup disc_mutex handling")
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: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/scsi/libfc/fc_disc.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/scsi/libfc/fc_disc.c
+++ b/drivers/scsi/libfc/fc_disc.c
@@ -294,9 +294,11 @@ static void fc_disc_done(struct fc_disc
 	 * discovery, reverify or log them in.	Otherwise, log them out.
 	 * Skip ports which were never discovered.  These are the dNS port
 	 * and ports which were created by PLOGI.
+	 *
+	 * We don't need to use the _rcu variant here as the rport list
+	 * is protected by the disc mutex which is already held on entry.
 	 */
-	rcu_read_lock();
-	list_for_each_entry_rcu(rdata, &disc->rports, peers) {
+	list_for_each_entry(rdata, &disc->rports, peers) {
 		if (!kref_get_unless_zero(&rdata->kref))
 			continue;
 		if (rdata->disc_id) {
@@ -307,7 +309,6 @@ static void fc_disc_done(struct fc_disc
 		}
 		kref_put(&rdata->kref, fc_rport_destroy);
 	}
-	rcu_read_unlock();
 	mutex_unlock(&disc->disc_mutex);
 	disc->disc_callback(lport, event);
 	mutex_lock(&disc->disc_mutex);