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authorSteffen Maier <maier@linux.vnet.ibm.com>2017-10-13 15:40:07 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-11-02 09:54:48 +0100
commit75c5541046d43aef74916439e05c5e930bf1dc48 (patch)
tree44e244394b948617c655664deae8d1410e8f23c1
parentca6711747c5a1434219ae0bd6745864a618f68b3 (diff)
scsi: zfcp: fix erp_action use-before-initialize in REC action trace
commit ab31fd0ce65ec93828b617123792c1bb7c6dcc42 upstream. v4.10 commit 6f2ce1c6af37 ("scsi: zfcp: fix rport unblock race with LUN recovery") extended accessing parent pointer fields of struct zfcp_erp_action for tracing. If an erp_action has never been enqueued before, these parent pointer fields are uninitialized and NULL. Examples are zfcp objects freshly added to the parent object's children list, before enqueueing their first recovery subsequently. In zfcp_erp_try_rport_unblock(), we iterate such list. Accessing erp_action fields can cause a NULL pointer dereference. Since the kernel can read from lowcore on s390, it does not immediately cause a kernel page fault. Instead it can cause hangs on trying to acquire the wrong erp_action->adapter->dbf->rec_lock in zfcp_dbf_rec_action_lvl() ^bogus^ while holding already other locks with IRQs disabled. Real life example from attaching lots of LUNs in parallel on many CPUs: crash> bt 17723 PID: 17723 TASK: ... CPU: 25 COMMAND: "zfcperp0.0.1800" LOWCORE INFO: -psw : 0x0404300180000000 0x000000000038e424 -function : _raw_spin_lock_wait_flags at 38e424 ... #0 [fdde8fc90] zfcp_dbf_rec_action_lvl at 3e0004e9862 [zfcp] #1 [fdde8fce8] zfcp_erp_try_rport_unblock at 3e0004dfddc [zfcp] #2 [fdde8fd38] zfcp_erp_strategy at 3e0004e0234 [zfcp] #3 [fdde8fda8] zfcp_erp_thread at 3e0004e0a12 [zfcp] #4 [fdde8fe60] kthread at 173550 #5 [fdde8feb8] kernel_thread_starter at 10add2 zfcp_adapter zfcp_port zfcp_unit <address>, 0x404040d600000000 scsi_device NULL, returning early! zfcp_scsi_dev.status = 0x40000000 0x40000000 ZFCP_STATUS_COMMON_RUNNING crash> zfcp_unit <address> struct zfcp_unit { erp_action = { adapter = 0x0, port = 0x0, unit = 0x0, }, } zfcp_erp_action is always fully embedded into its container object. Such container object is never moved in its object tree (only add or delete). Hence, erp_action parent pointers can never change. To fix the issue, initialize the erp_action parent pointers before adding the erp_action container to any list and thus before it becomes accessible from outside of its initializing function. In order to also close the time window between zfcp_erp_setup_act() memsetting the entire erp_action to zero and setting the parent pointers again, drop the memset and instead explicitly initialize individually all erp_action fields except for parent pointers. To be extra careful not to introduce any other unintended side effect, even keep zeroing the erp_action fields for list and timer. Also double-check with WARN_ON_ONCE that erp_action parent pointers never change, so we get to know when we would deviate from previous behavior. Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com> Fixes: 6f2ce1c6af37 ("scsi: zfcp: fix rport unblock race with LUN recovery") Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/s390/scsi/zfcp_aux.c5
-rw-r--r--drivers/s390/scsi/zfcp_erp.c18
-rw-r--r--drivers/s390/scsi/zfcp_scsi.c5
3 files changed, 21 insertions, 7 deletions
diff --git a/drivers/s390/scsi/zfcp_aux.c b/drivers/s390/scsi/zfcp_aux.c
index bcc8f3dfd4c4..b3f9243cfed5 100644
--- a/drivers/s390/scsi/zfcp_aux.c
+++ b/drivers/s390/scsi/zfcp_aux.c
@@ -358,6 +358,8 @@ struct zfcp_adapter *zfcp_adapter_enqueue(struct ccw_device *ccw_device)
adapter->next_port_scan = jiffies;
+ adapter->erp_action.adapter = adapter;
+
if (zfcp_qdio_setup(adapter))
goto failed;
@@ -514,6 +516,9 @@ struct zfcp_port *zfcp_port_enqueue(struct zfcp_adapter *adapter, u64 wwpn,
port->dev.groups = zfcp_port_attr_groups;
port->dev.release = zfcp_port_release;
+ port->erp_action.adapter = adapter;
+ port->erp_action.port = port;
+
if (dev_set_name(&port->dev, "0x%016llx", (unsigned long long)wwpn)) {
kfree(port);
goto err_out;
diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c
index 7ccfce559034..3b23d6754598 100644
--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -193,9 +193,8 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need, u32 act_status,
atomic_or(ZFCP_STATUS_COMMON_ERP_INUSE,
&zfcp_sdev->status);
erp_action = &zfcp_sdev->erp_action;
- memset(erp_action, 0, sizeof(struct zfcp_erp_action));
- erp_action->port = port;
- erp_action->sdev = sdev;
+ WARN_ON_ONCE(erp_action->port != port);
+ WARN_ON_ONCE(erp_action->sdev != sdev);
if (!(atomic_read(&zfcp_sdev->status) &
ZFCP_STATUS_COMMON_RUNNING))
act_status |= ZFCP_STATUS_ERP_CLOSE_ONLY;
@@ -208,8 +207,8 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need, u32 act_status,
zfcp_erp_action_dismiss_port(port);
atomic_or(ZFCP_STATUS_COMMON_ERP_INUSE, &port->status);
erp_action = &port->erp_action;
- memset(erp_action, 0, sizeof(struct zfcp_erp_action));
- erp_action->port = port;
+ WARN_ON_ONCE(erp_action->port != port);
+ WARN_ON_ONCE(erp_action->sdev != NULL);
if (!(atomic_read(&port->status) & ZFCP_STATUS_COMMON_RUNNING))
act_status |= ZFCP_STATUS_ERP_CLOSE_ONLY;
break;
@@ -219,7 +218,8 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need, u32 act_status,
zfcp_erp_action_dismiss_adapter(adapter);
atomic_or(ZFCP_STATUS_COMMON_ERP_INUSE, &adapter->status);
erp_action = &adapter->erp_action;
- memset(erp_action, 0, sizeof(struct zfcp_erp_action));
+ WARN_ON_ONCE(erp_action->port != NULL);
+ WARN_ON_ONCE(erp_action->sdev != NULL);
if (!(atomic_read(&adapter->status) &
ZFCP_STATUS_COMMON_RUNNING))
act_status |= ZFCP_STATUS_ERP_CLOSE_ONLY;
@@ -229,7 +229,11 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need, u32 act_status,
return NULL;
}
- erp_action->adapter = adapter;
+ WARN_ON_ONCE(erp_action->adapter != adapter);
+ memset(&erp_action->list, 0, sizeof(erp_action->list));
+ memset(&erp_action->timer, 0, sizeof(erp_action->timer));
+ erp_action->step = ZFCP_ERP_STEP_UNINITIALIZED;
+ erp_action->fsf_req_id = 0;
erp_action->action = need;
erp_action->status = act_status;
diff --git a/drivers/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c
index a1eeeaaa0fca..1c11b8402b41 100644
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -115,10 +115,15 @@ static int zfcp_scsi_slave_alloc(struct scsi_device *sdev)
struct zfcp_unit *unit;
int npiv = adapter->connection_features & FSF_FEATURE_NPIV_MODE;
+ zfcp_sdev->erp_action.adapter = adapter;
+ zfcp_sdev->erp_action.sdev = sdev;
+
port = zfcp_get_port_by_wwpn(adapter, rport->port_name);
if (!port)
return -ENXIO;
+ zfcp_sdev->erp_action.port = port;
+
unit = zfcp_unit_find(port, zfcp_scsi_dev_lun(sdev));
if (unit)
put_device(&unit->dev);