From 65f8da475995f667af5298c644707dbd9d646ca6 Mon Sep 17 00:00:00 2001 From: Stefan Weinhuber Date: Wed, 20 Apr 2011 10:15:30 +0200 Subject: [S390] dasd: fix race between open and offline The dasd_open function uses the private_data pointer of the gendisk to find the dasd_block structure that matches the gendisk. When a DASD device is set offline, we set the private_data pointer of the gendisk to NULL and later remove the dasd_block structure, but there is still a small race window, in which dasd_open could first read a pointer from the private_data field and then try to use it, after the structure has already been freed. To close this race window, we will store a pointer to the dasd_devmap structure of the base device in the private_data field. The devmap entries are not deleted, and we already have proper locking and reference counting in place, so that we can safely get from a devmap pointer to the dasd_device and dasd_block structures of the device. Signed-off-by: Stefan Weinhuber Signed-off-by: Martin Schwidefsky --- drivers/s390/block/dasd_devmap.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'drivers/s390/block/dasd_devmap.c') diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c index 42e1bf35f689..d71511c7850a 100644 --- a/drivers/s390/block/dasd_devmap.c +++ b/drivers/s390/block/dasd_devmap.c @@ -674,6 +674,36 @@ dasd_device_from_cdev(struct ccw_device *cdev) return device; } +void dasd_add_link_to_gendisk(struct gendisk *gdp, struct dasd_device *device) +{ + struct dasd_devmap *devmap; + + devmap = dasd_find_busid(dev_name(&device->cdev->dev)); + if (IS_ERR(devmap)) + return; + spin_lock(&dasd_devmap_lock); + gdp->private_data = devmap; + spin_unlock(&dasd_devmap_lock); +} + +struct dasd_device *dasd_device_from_gendisk(struct gendisk *gdp) +{ + struct dasd_device *device; + struct dasd_devmap *devmap; + + if (!gdp->private_data) + return NULL; + device = NULL; + spin_lock(&dasd_devmap_lock); + devmap = gdp->private_data; + if (devmap && devmap->device) { + device = devmap->device; + dasd_get_device(device); + } + spin_unlock(&dasd_devmap_lock); + return device; +} + /* * SECTION: files in sysfs */ -- cgit v1.2.3