[PATCH 03/19] s390/dasd: Guard sysfs discipline callbacks against unallocated private data

[Stefan Haberland <sth@linux.ibm.com>]

Several sysfs show/store handlers call a discipline callback that
dereferences device->private, either directly or through the
DASD_DEFINE_ATTR() macro. During dasd_generic_set_online() the discipline
is assigned before check_device() allocates device->private, so an
unprivileged read of one of these world-readable attributes in that window
dereferences a NULL pointer and panics.

Guard the dereference inside each callback that actually touches
device->private.

Fixes: c729696bcf8b ("s390/dasd: Recognise data for ESE volumes")
Cc: stable@vger.kernel.org
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_eckd.c | 40 ++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index d356a9f8f016..b64ca714b53e 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -1492,6 +1492,8 @@ static void dasd_eckd_reset_path(struct dasd_device *device, __u8 pm)
 	struct dasd_eckd_private *private = device->private;
 	unsigned long flags;
 
+	if (!private)
+		return;
 	if (!private->fcx_max_data)
 		private->fcx_max_data = get_fcx_max_data(device);
 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
@@ -1647,6 +1649,9 @@ static int dasd_eckd_is_ese(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->vsq.vol_info.ese;
 }
 
@@ -1654,6 +1659,9 @@ static int dasd_eckd_ext_pool_id(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->vsq.extent_pool_id;
 }
 
@@ -1667,6 +1675,9 @@ static int dasd_eckd_space_configured(struct dasd_device *device)
 	struct dasd_eckd_private *private = device->private;
 	int rc;
 
+	if (!private)
+		return 0;
+
 	rc = dasd_eckd_read_vol_info(device);
 
 	return rc ? : private->vsq.space_configured;
@@ -1681,6 +1692,9 @@ static int dasd_eckd_space_allocated(struct dasd_device *device)
 	struct dasd_eckd_private *private = device->private;
 	int rc;
 
+	if (!private)
+		return 0;
+
 	rc = dasd_eckd_read_vol_info(device);
 
 	return rc ? : private->vsq.space_allocated;
@@ -1690,6 +1704,9 @@ static int dasd_eckd_logical_capacity(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->vsq.logical_capacity;
 }
 
@@ -1832,7 +1849,11 @@ static int dasd_eckd_read_ext_pool_info(struct dasd_device *device)
 static int dasd_eckd_ext_size(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
-	struct dasd_ext_pool_sum eps = private->eps;
+	struct dasd_ext_pool_sum eps;
+
+	if (!private)
+		return 0;
+	eps = private->eps;
 
 	if (!eps.flags.extent_size_valid)
 		return 0;
@@ -1848,6 +1869,9 @@ static int dasd_eckd_ext_pool_warn_thrshld(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->eps.warn_thrshld;
 }
 
@@ -1855,6 +1879,9 @@ static int dasd_eckd_ext_pool_cap_at_warnlevel(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->eps.flags.capacity_at_warnlevel;
 }
 
@@ -1865,6 +1892,9 @@ static int dasd_eckd_ext_pool_oos(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->eps.flags.pool_oos;
 }
 
@@ -5938,8 +5968,11 @@ static int dasd_eckd_query_host_access(struct dasd_device *device,
 	struct ccw1 *ccw;
 	int rc;
 
+	if (!private)
+		return -ENODEV;
+
 	/* not available for HYPER PAV alias devices */
-	if (!device->block && private->lcu->pav == HYPER_PAV)
+	if (!device->block && private->lcu && private->lcu->pav == HYPER_PAV)
 		return -EOPNOTSUPP;
 
 	/* may not be supported by the storage server */
@@ -6804,6 +6837,9 @@ static int dasd_eckd_hpf_enabled(struct dasd_device *device)
 {
 	struct dasd_eckd_private *private = device->private;
 
+	if (!private)
+		return 0;
+
 	return private->fcx_max_data ? 1 : 0;
 }
 
-- 
2.53.0