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Message-Id: <20201117122110.773594142@linuxfoundation.org>
Date: Tue, 17 Nov 2020 14:05:00 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Brian Bunker <brian@...estorage.com>,
Jitendra Khasdev <jitendra.khasdev@...cle.com>,
Hannes Reinecke <hare@...e.de>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 34/78] scsi: scsi_dh_alua: Avoid crash during alua_bus_detach()
From: Hannes Reinecke <hare@...e.de>
[ Upstream commit 5faf50e9e9fdc2117c61ff7e20da49cd6a29e0ca ]
alua_bus_detach() might be running concurrently with alua_rtpg_work(), so
we might trip over h->sdev == NULL and call BUG_ON(). The correct way of
handling it is to not set h->sdev to NULL in alua_bus_detach(), and call
rcu_synchronize() before the final delete to ensure that all concurrent
threads have left the critical section. Then we can get rid of the
BUG_ON() and replace it with a simple if condition.
Link: https://lore.kernel.org/r/1600167537-12509-1-git-send-email-jitendra.khasdev@oracle.com
Link: https://lore.kernel.org/r/20200924104559.26753-1-hare@suse.de
Cc: Brian Bunker <brian@...estorage.com>
Acked-by: Brian Bunker <brian@...estorage.com>
Tested-by: Jitendra Khasdev <jitendra.khasdev@...cle.com>
Reviewed-by: Jitendra Khasdev <jitendra.khasdev@...cle.com>
Signed-off-by: Hannes Reinecke <hare@...e.de>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/scsi/device_handler/scsi_dh_alua.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 60c288526355a..2bc3dc6244a5e 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -657,8 +657,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
rcu_read_lock();
list_for_each_entry_rcu(h,
&tmp_pg->dh_list, node) {
- /* h->sdev should always be valid */
- BUG_ON(!h->sdev);
+ if (!h->sdev)
+ continue;
h->sdev->access_state = desc[0];
}
rcu_read_unlock();
@@ -704,7 +704,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
pg->expiry = 0;
rcu_read_lock();
list_for_each_entry_rcu(h, &pg->dh_list, node) {
- BUG_ON(!h->sdev);
+ if (!h->sdev)
+ continue;
h->sdev->access_state =
(pg->state & SCSI_ACCESS_STATE_MASK);
if (pg->pref)
@@ -1149,7 +1150,6 @@ static void alua_bus_detach(struct scsi_device *sdev)
spin_lock(&h->pg_lock);
pg = h->pg;
rcu_assign_pointer(h->pg, NULL);
- h->sdev = NULL;
spin_unlock(&h->pg_lock);
if (pg) {
spin_lock_irq(&pg->lock);
@@ -1158,6 +1158,7 @@ static void alua_bus_detach(struct scsi_device *sdev)
kref_put(&pg->kref, release_port_group);
}
sdev->handler_data = NULL;
+ synchronize_rcu();
kfree(h);
}
--
2.27.0
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