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tcmu: fix crash during device removal 

We currently do

tcmu_free_device ->tcmu_netlink_event(TCMU_CMD_REMOVED_DEVICE) ->
uio_unregister_device -> kfree(tcmu_dev).

The problem is that the kernel does not wait for userspace to
do the close() on the uio device before freeing the tcmu_dev.
We can then hit a race where the kernel frees the tcmu_dev before
userspace does close() and so when close() -> release -> tcmu_release
is done, we try to access a freed tcmu_dev.

This patch made over the target-pending master branch moves the freeing
of the tcmu_dev to when the last reference has been dropped.

This also fixes a leak where if tcmu_configure_device was not called on a
device we did not free udev->name which was allocated at tcmu_alloc_device time.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Mike Christie 2017-05-17 04:34:37 -05:00 committed by Nicholas Bellinger
parent 4ff83daa02
commit f3cdbe39b2
1 changed files with 33 additions and 13 deletions
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46
drivers/target/target_core_user.c
View File

@ -97,7 +97,7 @@ struct tcmu_hba {
struct tcmu_dev {
struct list_head node;
struct kref kref;
struct se_device se_dev;
char *name;
@ -969,6 +969,7 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
udev = kzalloc(sizeof(struct tcmu_dev), GFP_KERNEL);
if (!udev)
return NULL;
kref_init(&udev->kref);
udev->name = kstrdup(name, GFP_KERNEL);
if (!udev->name) {
@ -1145,6 +1146,24 @@ static int tcmu_open(struct uio_info *info, struct inode *inode)
return 0;
}
static void tcmu_dev_call_rcu(struct rcu_head *p)
{
struct se_device *dev = container_of(p, struct se_device, rcu_head);
struct tcmu_dev *udev = TCMU_DEV(dev);
kfree(udev->uio_info.name);
kfree(udev->name);
kfree(udev);
}
static void tcmu_dev_kref_release(struct kref *kref)
{
struct tcmu_dev *udev = container_of(kref, struct tcmu_dev, kref);
struct se_device *dev = &udev->se_dev;
call_rcu(&dev->rcu_head, tcmu_dev_call_rcu);
}
static int tcmu_release(struct uio_info *info, struct inode *inode)
{
struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);
@ -1152,7 +1171,8 @@ static int tcmu_release(struct uio_info *info, struct inode *inode)
clear_bit(TCMU_DEV_BIT_OPEN, &udev->flags);
pr_debug("close\n");
/* release ref from configure */
kref_put(&udev->kref, tcmu_dev_kref_release);
return 0;
}
@ -1272,6 +1292,12 @@ static int tcmu_configure_device(struct se_device *dev)
dev->dev_attrib.hw_max_sectors = 128;
dev->dev_attrib.hw_queue_depth = 128;
/*
* Get a ref incase userspace does a close on the uio device before
* LIO has initiated tcmu_free_device.
*/
kref_get(&udev->kref);
ret = tcmu_netlink_event(TCMU_CMD_ADDED_DEVICE, udev->uio_info.name,
udev->uio_info.uio_dev->minor);
if (ret)
@ -1284,11 +1310,13 @@ static int tcmu_configure_device(struct se_device *dev)
return 0;
err_netlink:
kref_put(&udev->kref, tcmu_dev_kref_release);
uio_unregister_device(&udev->uio_info);
err_register:
vfree(udev->mb_addr);
err_vzalloc:
kfree(info->name);
info->name = NULL;
return ret;
}
@ -1302,14 +1330,6 @@ static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
return -EINVAL;
}
static void tcmu_dev_call_rcu(struct rcu_head *p)
{
struct se_device *dev = container_of(p, struct se_device, rcu_head);
struct tcmu_dev *udev = TCMU_DEV(dev);
kfree(udev);
}
static bool tcmu_dev_configured(struct tcmu_dev *udev)
{
return udev->uio_info.uio_dev ? true : false;
@ -1364,10 +1384,10 @@ static void tcmu_free_device(struct se_device *dev)
udev->uio_info.uio_dev->minor);
uio_unregister_device(&udev->uio_info);
kfree(udev->uio_info.name);
kfree(udev->name);
}
call_rcu(&dev->rcu_head, tcmu_dev_call_rcu);
/* release ref from init */
kref_put(&udev->kref, tcmu_dev_kref_release);
}
enum {