[PATCH v5 02/17] 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
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_eckd.c | 38 +++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index 073795ea7cd0..5593013c9db2 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -1491,6 +1491,8 @@ 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);
@@ -1646,6 +1648,9 @@ 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;
 }
 
@@ -1653,6 +1658,9 @@ 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;
 }
 
@@ -1666,6 +1674,9 @@ 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;
@@ -1680,6 +1691,9 @@ 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;
@@ -1689,6 +1703,9 @@ 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;
 }
 
@@ -1831,7 +1848,11 @@ 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;
@@ -1847,6 +1868,9 @@ 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;
 }
 
@@ -1854,6 +1878,9 @@ 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;
 }
 
@@ -1864,6 +1891,9 @@ 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;
 }
 
@@ -5935,6 +5965,9 @@ 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)
 		return -EOPNOTSUPP;
@@ -6801,6 +6834,9 @@ 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