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5715c4dd66
In following sequences, child devices created while removing mdev parent
device can be left out, or it may lead to race of removing half
initialized child mdev devices.
issue-1:
--------
cpu-0 cpu-1
----- -----
mdev_unregister_device()
device_for_each_child()
mdev_device_remove_cb()
mdev_device_remove()
create_store()
mdev_device_create() [...]
device_add()
parent_remove_sysfs_files()
/* BUG: device added by cpu-0
* whose parent is getting removed
* and it won't process this mdev.
*/
issue-2:
--------
Below crash is observed when user initiated remove is in progress
and mdev_unregister_driver() completes parent unregistration.
cpu-0 cpu-1
----- -----
remove_store()
mdev_device_remove()
active = false;
mdev_unregister_device()
parent device removed.
[...]
parents->ops->remove()
/*
* BUG: Accessing invalid parent.
*/
This is similar race like create() racing with mdev_unregister_device().
BUG: unable to handle kernel paging request at ffffffffc0585668
PGD e8f618067 P4D e8f618067 PUD e8f61a067 PMD 85adca067 PTE 0
Oops: 0000 [#1] SMP PTI
CPU: 41 PID: 37403 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6
Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016
RIP: 0010:mdev_device_remove+0xfa/0x140 [mdev]
Call Trace:
remove_store+0x71/0x90 [mdev]
kernfs_fop_write+0x113/0x1a0
vfs_write+0xad/0x1b0
ksys_write+0x5a/0xe0
do_syscall_64+0x5a/0x210
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Therefore, mdev core is improved as below to overcome above issues.
Wait for any ongoing mdev create() and remove() to finish before
unregistering parent device.
This continues to allow multiple create and remove to progress in
parallel for different mdev devices as most common case.
At the same time guard parent removal while parent is being accessed by
create() and remove() callbacks.
create()/remove() and unregister_device() are synchronized by the rwsem.
Refactor device removal code to mdev_device_remove_common() to avoid
acquiring unreg_sem of the parent.
Fixes: 7b96953bc6 ("vfio: Mediated device Core driver")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
68 lines
1.8 KiB
C
68 lines
1.8 KiB
C
/*
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* Mediated device interal definitions
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*
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* Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
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* Author: Neo Jia <cjia@nvidia.com>
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* Kirti Wankhede <kwankhede@nvidia.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef MDEV_PRIVATE_H
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#define MDEV_PRIVATE_H
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int mdev_bus_register(void);
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void mdev_bus_unregister(void);
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struct mdev_parent {
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struct device *dev;
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const struct mdev_parent_ops *ops;
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struct kref ref;
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struct list_head next;
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struct kset *mdev_types_kset;
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struct list_head type_list;
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/* Synchronize device creation/removal with parent unregistration */
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struct rw_semaphore unreg_sem;
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};
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struct mdev_device {
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struct device dev;
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struct mdev_parent *parent;
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guid_t uuid;
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void *driver_data;
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struct list_head next;
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struct kobject *type_kobj;
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struct device *iommu_device;
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bool active;
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};
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#define to_mdev_device(dev) container_of(dev, struct mdev_device, dev)
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#define dev_is_mdev(d) ((d)->bus == &mdev_bus_type)
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struct mdev_type {
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struct kobject kobj;
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struct kobject *devices_kobj;
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struct mdev_parent *parent;
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struct list_head next;
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struct attribute_group *group;
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};
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#define to_mdev_type_attr(_attr) \
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container_of(_attr, struct mdev_type_attribute, attr)
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#define to_mdev_type(_kobj) \
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container_of(_kobj, struct mdev_type, kobj)
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int parent_create_sysfs_files(struct mdev_parent *parent);
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void parent_remove_sysfs_files(struct mdev_parent *parent);
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int mdev_create_sysfs_files(struct device *dev, struct mdev_type *type);
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void mdev_remove_sysfs_files(struct device *dev, struct mdev_type *type);
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int mdev_device_create(struct kobject *kobj,
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struct device *dev, const guid_t *uuid);
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int mdev_device_remove(struct device *dev);
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#endif /* MDEV_PRIVATE_H */
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