[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 <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 4d2df2f..475e603 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2314,15 +2314,14 @@
static int dasd_open(struct block_device *bdev, fmode_t mode)
{
- struct dasd_block *block = bdev->bd_disk->private_data;
struct dasd_device *base;
int rc;
- if (!block)
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
return -ENODEV;
- base = block->base;
- atomic_inc(&block->open_count);
+ atomic_inc(&base->block->open_count);
if (test_bit(DASD_FLAG_OFFLINE, &base->flags)) {
rc = -ENODEV;
goto unlock;
@@ -2355,21 +2354,28 @@
goto out;
}
+ dasd_put_device(base);
return 0;
out:
module_put(base->discipline->owner);
unlock:
- atomic_dec(&block->open_count);
+ atomic_dec(&base->block->open_count);
+ dasd_put_device(base);
return rc;
}
static int dasd_release(struct gendisk *disk, fmode_t mode)
{
- struct dasd_block *block = disk->private_data;
+ struct dasd_device *base;
- atomic_dec(&block->open_count);
- module_put(block->base->discipline->owner);
+ base = dasd_device_from_gendisk(disk);
+ if (!base)
+ return -ENODEV;
+
+ atomic_dec(&base->block->open_count);
+ module_put(base->discipline->owner);
+ dasd_put_device(base);
return 0;
}
@@ -2378,20 +2384,20 @@
*/
static int dasd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
- struct dasd_block *block;
struct dasd_device *base;
- block = bdev->bd_disk->private_data;
- if (!block)
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
return -ENODEV;
- base = block->base;
if (!base->discipline ||
- !base->discipline->fill_geometry)
+ !base->discipline->fill_geometry) {
+ dasd_put_device(base);
return -EINVAL;
-
- base->discipline->fill_geometry(block, geo);
- geo->start = get_start_sect(bdev) >> block->s2b_shift;
+ }
+ base->discipline->fill_geometry(base->block, geo);
+ geo->start = get_start_sect(bdev) >> base->block->s2b_shift;
+ dasd_put_device(base);
return 0;
}
@@ -2528,7 +2534,6 @@
dasd_set_target_state(device, DASD_STATE_NEW);
/* dasd_delete_device destroys the device reference. */
block = device->block;
- device->block = NULL;
dasd_delete_device(device);
/*
* life cycle of block is bound to device, so delete it after
@@ -2650,7 +2655,6 @@
dasd_set_target_state(device, DASD_STATE_NEW);
/* dasd_delete_device destroys the device reference. */
block = device->block;
- device->block = NULL;
dasd_delete_device(device);
/*
* life cycle of block is bound to device, so delete it after
diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
index 42e1bf3..d71511c 100644
--- a/drivers/s390/block/dasd_devmap.c
+++ b/drivers/s390/block/dasd_devmap.c
@@ -674,6 +674,36 @@
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
*/
diff --git a/drivers/s390/block/dasd_genhd.c b/drivers/s390/block/dasd_genhd.c
index 5505bc0..19a1ff0 100644
--- a/drivers/s390/block/dasd_genhd.c
+++ b/drivers/s390/block/dasd_genhd.c
@@ -73,7 +73,7 @@
if (base->features & DASD_FEATURE_READONLY ||
test_bit(DASD_FLAG_DEVICE_RO, &base->flags))
set_disk_ro(gdp, 1);
- gdp->private_data = block;
+ dasd_add_link_to_gendisk(gdp, base);
gdp->queue = block->request_queue;
block->gdp = gdp;
set_capacity(block->gdp, 0);
diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index df9f699..d1e4f2c 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -686,6 +686,9 @@
struct dasd_device *dasd_device_from_cdev_locked(struct ccw_device *);
struct dasd_device *dasd_device_from_devindex(int);
+void dasd_add_link_to_gendisk(struct gendisk *, struct dasd_device *);
+struct dasd_device *dasd_device_from_gendisk(struct gendisk *);
+
int dasd_parse(void);
int dasd_busid_known(const char *);
diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
index 26075e9..72261e4 100644
--- a/drivers/s390/block/dasd_ioctl.c
+++ b/drivers/s390/block/dasd_ioctl.c
@@ -42,16 +42,22 @@
static int
dasd_ioctl_enable(struct block_device *bdev)
{
- struct dasd_block *block = bdev->bd_disk->private_data;
+ struct dasd_device *base;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
- dasd_enable_device(block->base);
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
+ return -ENODEV;
+
+ dasd_enable_device(base);
/* Formatting the dasd device can change the capacity. */
mutex_lock(&bdev->bd_mutex);
- i_size_write(bdev->bd_inode, (loff_t)get_capacity(block->gdp) << 9);
+ i_size_write(bdev->bd_inode,
+ (loff_t)get_capacity(base->block->gdp) << 9);
mutex_unlock(&bdev->bd_mutex);
+ dasd_put_device(base);
return 0;
}
@@ -62,11 +68,14 @@
static int
dasd_ioctl_disable(struct block_device *bdev)
{
- struct dasd_block *block = bdev->bd_disk->private_data;
+ struct dasd_device *base;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
+ return -ENODEV;
/*
* Man this is sick. We don't do a real disable but only downgrade
* the device to DASD_STATE_BASIC. The reason is that dasdfmt uses
@@ -75,7 +84,7 @@
* using the BIODASDFMT ioctl. Therefore the correct state for the
* device is DASD_STATE_BASIC that allows to do basic i/o.
*/
- dasd_set_target_state(block->base, DASD_STATE_BASIC);
+ dasd_set_target_state(base, DASD_STATE_BASIC);
/*
* Set i_size to zero, since read, write, etc. check against this
* value.
@@ -83,6 +92,7 @@
mutex_lock(&bdev->bd_mutex);
i_size_write(bdev->bd_inode, 0);
mutex_unlock(&bdev->bd_mutex);
+ dasd_put_device(base);
return 0;
}
@@ -191,26 +201,36 @@
static int
dasd_ioctl_format(struct block_device *bdev, void __user *argp)
{
- struct dasd_block *block = bdev->bd_disk->private_data;
+ struct dasd_device *base;
struct format_data_t fdata;
+ int rc;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
if (!argp)
return -EINVAL;
-
- if (block->base->features & DASD_FEATURE_READONLY ||
- test_bit(DASD_FLAG_DEVICE_RO, &block->base->flags))
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
+ return -ENODEV;
+ if (base->features & DASD_FEATURE_READONLY ||
+ test_bit(DASD_FLAG_DEVICE_RO, &base->flags)) {
+ dasd_put_device(base);
return -EROFS;
- if (copy_from_user(&fdata, argp, sizeof(struct format_data_t)))
+ }
+ if (copy_from_user(&fdata, argp, sizeof(struct format_data_t))) {
+ dasd_put_device(base);
return -EFAULT;
+ }
if (bdev != bdev->bd_contains) {
pr_warning("%s: The specified DASD is a partition and cannot "
"be formatted\n",
- dev_name(&block->base->cdev->dev));
+ dev_name(&base->cdev->dev));
+ dasd_put_device(base);
return -EINVAL;
}
- return dasd_format(block, &fdata);
+ rc = dasd_format(base->block, &fdata);
+ dasd_put_device(base);
+ return rc;
}
#ifdef CONFIG_DASD_PROFILE
@@ -340,8 +360,8 @@
static int
dasd_ioctl_set_ro(struct block_device *bdev, void __user *argp)
{
- struct dasd_block *block = bdev->bd_disk->private_data;
- int intval;
+ struct dasd_device *base;
+ int intval, rc;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
@@ -350,10 +370,17 @@
return -EINVAL;
if (get_user(intval, (int __user *)argp))
return -EFAULT;
- if (!intval && test_bit(DASD_FLAG_DEVICE_RO, &block->base->flags))
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
+ return -ENODEV;
+ if (!intval && test_bit(DASD_FLAG_DEVICE_RO, &base->flags)) {
+ dasd_put_device(base);
return -EROFS;
+ }
set_disk_ro(bdev->bd_disk, intval);
- return dasd_set_feature(block->base->cdev, DASD_FEATURE_READONLY, intval);
+ rc = dasd_set_feature(base->cdev, DASD_FEATURE_READONLY, intval);
+ dasd_put_device(base);
+ return rc;
}
static int dasd_ioctl_readall_cmb(struct dasd_block *block, unsigned int cmd,
@@ -372,59 +399,78 @@
int dasd_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
- struct dasd_block *block = bdev->bd_disk->private_data;
+ struct dasd_block *block;
+ struct dasd_device *base;
void __user *argp;
+ int rc;
if (is_compat_task())
argp = compat_ptr(arg);
else
argp = (void __user *)arg;
- if (!block)
- return -ENODEV;
-
if ((_IOC_DIR(cmd) != _IOC_NONE) && !arg) {
PRINT_DEBUG("empty data ptr");
return -EINVAL;
}
+ base = dasd_device_from_gendisk(bdev->bd_disk);
+ if (!base)
+ return -ENODEV;
+ block = base->block;
+ rc = 0;
switch (cmd) {
case BIODASDDISABLE:
- return dasd_ioctl_disable(bdev);
+ rc = dasd_ioctl_disable(bdev);
+ break;
case BIODASDENABLE:
- return dasd_ioctl_enable(bdev);
+ rc = dasd_ioctl_enable(bdev);
+ break;
case BIODASDQUIESCE:
- return dasd_ioctl_quiesce(block);
+ rc = dasd_ioctl_quiesce(block);
+ break;
case BIODASDRESUME:
- return dasd_ioctl_resume(block);
+ rc = dasd_ioctl_resume(block);
+ break;
case BIODASDFMT:
- return dasd_ioctl_format(bdev, argp);
+ rc = dasd_ioctl_format(bdev, argp);
+ break;
case BIODASDINFO:
- return dasd_ioctl_information(block, cmd, argp);
+ rc = dasd_ioctl_information(block, cmd, argp);
+ break;
case BIODASDINFO2:
- return dasd_ioctl_information(block, cmd, argp);
+ rc = dasd_ioctl_information(block, cmd, argp);
+ break;
case BIODASDPRRD:
- return dasd_ioctl_read_profile(block, argp);
+ rc = dasd_ioctl_read_profile(block, argp);
+ break;
case BIODASDPRRST:
- return dasd_ioctl_reset_profile(block);
+ rc = dasd_ioctl_reset_profile(block);
+ break;
case BLKROSET:
- return dasd_ioctl_set_ro(bdev, argp);
+ rc = dasd_ioctl_set_ro(bdev, argp);
+ break;
case DASDAPIVER:
- return dasd_ioctl_api_version(argp);
+ rc = dasd_ioctl_api_version(argp);
+ break;
case BIODASDCMFENABLE:
- return enable_cmf(block->base->cdev);
+ rc = enable_cmf(base->cdev);
+ break;
case BIODASDCMFDISABLE:
- return disable_cmf(block->base->cdev);
+ rc = disable_cmf(base->cdev);
+ break;
case BIODASDREADALLCMB:
- return dasd_ioctl_readall_cmb(block, cmd, argp);
+ rc = dasd_ioctl_readall_cmb(block, cmd, argp);
+ break;
default:
/* if the discipline has an ioctl method try it. */
- if (block->base->discipline->ioctl) {
- int rval = block->base->discipline->ioctl(block, cmd, argp);
- if (rval != -ENOIOCTLCMD)
- return rval;
- }
-
- return -EINVAL;
+ if (base->discipline->ioctl) {
+ rc = base->discipline->ioctl(block, cmd, argp);
+ if (rc == -ENOIOCTLCMD)
+ rc = -EINVAL;
+ } else
+ rc = -EINVAL;
}
+ dasd_put_device(base);
+ return rc;
}