linux-stable.git/drivers/vfio/mdev/mdev_sysfs.c, branch linux-5.17.y

vfio/mdev: Correct the function signatures for the mdev_type_attributes

2021-04-12T16:36:00+00:00

The driver core standard is to pass in the properly typed object, the
properly typed attribute and the buffer data. It stems from the root
kobject method:

  ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr,..)

Each subclass of kobject should provide their own function with the same
signature but more specific types, eg struct device uses:

  ssize_t (*show)(struct device *dev, struct device_attribute *attr,..)

In this case the existing signature is:

  ssize_t (*show)(struct kobject *kobj, struct device *dev,..)

Where kobj is a 'struct mdev_type *' and dev is 'mdev_type->parent->dev'.

Change the mdev_type related sysfs attribute functions to:

  ssize_t (*show)(struct mdev_type *mtype, struct mdev_type_attribute *attr,..)

In order to restore type safety and match the driver core standard

There are no current users of 'attr', but if it is ever needed it would be
hard to add in retroactively, so do it now.

Reviewed-by: Kevin Tian 
Reviewed-by: Cornelia Huck 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jason Gunthorpe 
Message-Id: <18-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson

vfio/mdev: Add mdev/mtype_get_type_group_id()

2021-04-07T21:39:18+00:00

This returns the index in the supported_type_groups array that is
associated with the mdev_type attached to the struct mdev_device or its
containing struct kobject.

Each mdev_device can be spawned from exactly one mdev_type, which in turn
originates from exactly one supported_type_group.

Drivers are using weird string calculations to try and get back to this
index, providing a direct access to the index removes a bunch of wonky
driver code.

mdev_type->group can be deleted as the group is obtained using the
type_group_id.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Kevin Tian 
Reviewed-by: Cornelia Huck 
Signed-off-by: Jason Gunthorpe 
Message-Id: <11-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson

vfio/mdev: Add missing reference counting to mdev_type

2021-04-07T21:39:17+00:00

struct mdev_type holds a pointer to the kref'd object struct mdev_parent,
but doesn't hold the kref. The lifetime of the parent becomes implicit
because parent_remove_sysfs_files() is supposed to remove all the access
before the parent can be freed, but this is very hard to reason about.

Make it obviously correct by adding the missing get.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Kevin Tian 
Reviewed-by: Cornelia Huck 
Signed-off-by: Jason Gunthorpe 
Message-Id: <7-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson

vfio/mdev: Use struct mdev_type in struct mdev_device

2021-04-07T21:39:17+00:00

The kobj pointer in mdev_device is actually pointing at a struct
mdev_type. Use the proper type so things are understandable.

There are a number of places that are confused and passing both the mdev
and the mtype as function arguments, fix these to derive the mtype
directly from the mdev to remove the redundancy.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Kevin Tian 
Reviewed-by: Cornelia Huck 
Signed-off-by: Jason Gunthorpe 
Message-Id: <5-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson

vfio/mdev: Add missing typesafety around mdev_device

2021-04-07T21:39:16+00:00

The mdev API should accept and pass a 'struct mdev_device *' in all
places, not pass a 'struct device *' and cast it internally with
to_mdev_device(). Particularly in its struct mdev_driver functions, the
whole point of a bus's struct device_driver wrapper is to provide type
safety compared to the default struct device_driver.

Further, the driver core standard is for bus drivers to expose their
device structure in their public headers that can be used with
container_of() inlines and '&foo->dev' to go between the class levels, and
'&foo->dev' to be used with dev_err/etc driver core helper functions. Move
'struct mdev_device' to mdev.h

Once done this allows moving some one instruction exported functions to
static inlines, which in turns allows removing one of the two grotesque
symbol_get()'s related to mdev in the core code.

Reviewed-by: Kevin Tian 
Reviewed-by: Cornelia Huck 
Signed-off-by: Jason Gunthorpe 
Reviewed-by: Christoph Hellwig 
Message-Id: <3-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson

vfio/mdev: Do not allow a mdev_type to have a NULL parent pointer

2021-04-07T21:39:16+00:00

There is a small race where the parent is NULL even though the kobj has
already been made visible in sysfs.

For instance the attribute_group is made visible in sysfs_create_files()
and the mdev_type_attr_show() does:

    ret = attr->show(kobj, type->parent->dev, buf);

Which will crash on NULL parent. Move the parent setup to before the type
pointer leaves the stack frame.

Fixes: 7b96953bc640 ("vfio: Mediated device Core driver")
Reviewed-by: Christoph Hellwig 
Reviewed-by: Kevin Tian 
Reviewed-by: Max Gurtovoy 
Reviewed-by: Cornelia Huck 
Signed-off-by: Jason Gunthorpe 
Message-Id: <2-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson

vfio/mdev: Fix reference count leak in add_mdev_supported_type

2020-05-29T22:07:18+00:00

kobject_init_and_add() takes reference even when it fails.
If this function returns an error, kobject_put() must be called to
properly clean up the memory associated with the object. Thus,
replace kfree() by kobject_put() to fix this issue. Previous
commit "b8eb718348b8" fixed a similar problem.

Fixes: 7b96953bc640 ("vfio: Mediated device Core driver")
Signed-off-by: Qiushi Wu 
Reviewed-by: Cornelia Huck 
Reviewed-by: Kirti Wankhede 
Signed-off-by: Alex Williamson

vfio/mdev: make create attribute static

2020-01-09T18:30:57+00:00

The create attribute is not exported, so make it
static to avoid the following sparse warning:

drivers/vfio/mdev/mdev_sysfs.c:77:1: warning: symbol 'mdev_type_attr_create' was not declared. Should it be static?

Signed-off-by: Ben Dooks (Codethink) 
Reviewed-by: Cornelia Huck 
Signed-off-by: Alex Williamson

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55+00:00

Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Enrico Weigelt 
Reviewed-by: Kate Stewart 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman

vfio/mdev: Avoid creating sysfs remove file on stale device removal

2019-06-06T18:32:37+00:00

If device is removal is initiated by two threads as below, mdev core
attempts to create a syfs remove file on stale device.
During this flow, below [1] call trace is observed.

     cpu-0                                    cpu-1
     -----                                    -----
  mdev_unregister_device()
    device_for_each_child
       mdev_device_remove_cb
          mdev_device_remove
                                       user_syscall
                                         remove_store()
                                           mdev_device_remove()
                                        [..]
   unregister device();
                                       /* not found in list or
                                        * active=false.
                                        */
                                          sysfs_create_file()
                                          ..Call trace

Now that mdev core follows correct device removal sequence of the linux
bus model, remove shouldn't fail in normal cases. If it fails, there is
no point of creating a stale file or checking for specific error status.

kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327
sysfs_create_file_ns+0x7f/0x90
kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted
5.1.0-rc6-vdevbus+ #6
kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b
08/09/2016
kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90
kernel: Call Trace:
kernel: remove_store+0xdc/0x100 [mdev]
kernel: kernfs_fop_write+0x113/0x1a0
kernel: vfs_write+0xad/0x1b0
kernel: ksys_write+0x5a/0xe0
kernel: do_syscall_64+0x5a/0x210
kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe

Reviewed-by: Cornelia Huck 
Signed-off-by: Parav Pandit 
Signed-off-by: Alex Williamson