From c020d722b110a44c613ef71e657e6dd4116e09d9 Mon Sep 17 00:00:00 2001 From: Stefan Haberland Date: Tue, 20 Sep 2016 10:42:38 +0200 Subject: [PATCH] s390/dasd: fix panic during offline processing A DASD device consists of the device itself and a discipline with a corresponding private structure. These fields are set up during online processing right after the device is created and before it is processed by the state machine and made available for I/O. During offline processing the discipline pointer and the private data gets freed within the state machine and without protection of the existing reference count. This might lead to a kernel panic because a function might have taken a device reference and accesses the discipline pointer and/or private data of the device while this is already freed. Fix by freeing the discipline pointer and the private data after ensuring that there is no reference to the device left. Reviewed-by: Peter Oberparleiter Signed-off-by: Stefan Haberland Signed-off-by: Martin Schwidefsky --- drivers/s390/block/dasd.c | 26 ++++++++++++++++---------- drivers/s390/block/dasd_devmap.c | 1 + drivers/s390/block/dasd_int.h | 1 + 3 files changed, 18 insertions(+), 10 deletions(-) diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c index 706ae0ac94c9..1de089019268 100644 --- a/drivers/s390/block/dasd.c +++ b/drivers/s390/block/dasd.c @@ -212,16 +212,6 @@ static int dasd_state_known_to_new(struct dasd_device *device) { /* Disable extended error reporting for this device. */ dasd_eer_disable(device); - /* Forget the discipline information. */ - if (device->discipline) { - if (device->discipline->uncheck_device) - device->discipline->uncheck_device(device); - module_put(device->discipline->owner); - } - device->discipline = NULL; - if (device->base_discipline) - module_put(device->base_discipline->owner); - device->base_discipline = NULL; device->state = DASD_STATE_NEW; if (device->block) @@ -3377,6 +3367,22 @@ int dasd_generic_probe(struct ccw_device *cdev, } EXPORT_SYMBOL_GPL(dasd_generic_probe); +void dasd_generic_free_discipline(struct dasd_device *device) +{ + /* Forget the discipline information. */ + if (device->discipline) { + if (device->discipline->uncheck_device) + device->discipline->uncheck_device(device); + module_put(device->discipline->owner); + device->discipline = NULL; + } + if (device->base_discipline) { + module_put(device->base_discipline->owner); + device->base_discipline = NULL; + } +} +EXPORT_SYMBOL_GPL(dasd_generic_free_discipline); + /* * This will one day be called from a global not_oper handler. * It is also used by driver_unregister during module unload. diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c index 3cdbce45e464..15a1a70cace9 100644 --- a/drivers/s390/block/dasd_devmap.c +++ b/drivers/s390/block/dasd_devmap.c @@ -617,6 +617,7 @@ dasd_delete_device(struct dasd_device *device) /* Wait for reference counter to drop to zero. */ wait_event(dasd_delete_wq, atomic_read(&device->ref_count) == 0); + dasd_generic_free_discipline(device); /* Disconnect dasd_device structure from ccw_device structure. */ cdev = device->cdev; device->cdev = NULL; diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h index ac7027e6d52b..87ff6cef872f 100644 --- a/drivers/s390/block/dasd_int.h +++ b/drivers/s390/block/dasd_int.h @@ -725,6 +725,7 @@ void dasd_block_clear_timer(struct dasd_block *); int dasd_cancel_req(struct dasd_ccw_req *); int dasd_flush_device_queue(struct dasd_device *); int dasd_generic_probe (struct ccw_device *, struct dasd_discipline *); +void dasd_generic_free_discipline(struct dasd_device *); void dasd_generic_remove (struct ccw_device *cdev); int dasd_generic_set_online(struct ccw_device *, struct dasd_discipline *); int dasd_generic_set_offline (struct ccw_device *cdev); -- 2.30.2