From 71159b6ecb067565fb41faba616116e8c0fc10ea Mon Sep 17 00:00:00 2001 From: Benjamin Block Date: Fri, 8 May 2020 19:23:34 +0200 Subject: scsi: zfcp: Fence early sysfs interfaces for accesses of shost objects When setting an adapter online for the first time, we also create a couple of entries for it in the sysfs device tree. This is also true even if the adapter has not yet ever gone successfully through exchange config and exchange port data. When moving the scsi host object allocation and registration to after the first exchange config and exchange port data, this make the `port_rescan` attribute susceptible to invalid pointer-dereferences of the shost field before the adapter is fully initialized. When written to, it schedules a `scan_work` item that will in turn make use of the associated fibre channel host object to check the topology used for this FCP device. Because scanning for remote ports can't be done successfully without completing exchange config and exchange port data first, we can simply fence `port_rescan`, and so prevent the illegal access. As with cases where we can't get a reference to the adapter, we also return -ENODEV here. Applications need to handle that errno today already. After a successful allocation of the scsi host object nothing changes in the work flow. Link: https://lore.kernel.org/r/ef65366d309993ca91b6917727590ca7ca166c8f.1588956679.git.bblock@linux.ibm.com Reviewed-by: Steffen Maier Signed-off-by: Benjamin Block Signed-off-by: Martin K. Petersen --- drivers/s390/scsi/zfcp_sysfs.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'drivers/s390') diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c index 7ec30ded0169..8d9662e8b717 100644 --- a/drivers/s390/scsi/zfcp_sysfs.c +++ b/drivers/s390/scsi/zfcp_sysfs.c @@ -216,10 +216,22 @@ static ssize_t zfcp_sysfs_port_rescan_store(struct device *dev, { struct ccw_device *cdev = to_ccwdev(dev); struct zfcp_adapter *adapter = zfcp_ccw_adapter_by_cdev(cdev); + int retval = 0; if (!adapter) return -ENODEV; + /* + * If `scsi_host` is missing, we can't schedule `scan_work`, as it + * makes use of the corresponding fc_host object. But this state is + * only possible if xconfig/xport data has never completed yet, + * and we couldn't successfully scan for ports anyway. + */ + if (adapter->scsi_host == NULL) { + retval = -ENODEV; + goto out; + } + /* * Users wish is our command: immediately schedule and flush a * worker to conduct a synchronous port scan, that is, neither @@ -227,9 +239,9 @@ static ssize_t zfcp_sysfs_port_rescan_store(struct device *dev, */ queue_delayed_work(adapter->work_queue, &adapter->scan_work, 0); flush_delayed_work(&adapter->scan_work); +out: zfcp_ccw_adapter_put(adapter); - - return (ssize_t) count; + return retval ? retval : (ssize_t) count; } static ZFCP_DEV_ATTR(adapter, port_rescan, S_IWUSR, NULL, zfcp_sysfs_port_rescan_store); -- cgit v1.2.3-59-g8ed1b