[PATCH 33/34] vfio/mdev: Use the driver core to create the 'remove' file

Christoph Hellwig
2022-04-11T14:17:37Z

From: Jason Gunthorpe <jgg@nvidia.com>

The device creator is supposed to use the dev.groups value to add sysfs
files before device_add is called, not call sysfs_create_files() after
device_add() returns. This creates a race with uevent delivery where the
extra attribute will not be visible.

This was being done because the groups had been co-opted by the mdev
driver, now that prior patches have moved the driver's groups to the
struct device_driver the dev.group is properly free for use here.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/vfio/mdev/mdev_core.c | 1 +
drivers/vfio/mdev/mdev_private.h | 2 ++
drivers/vfio/mdev/mdev_sysfs.c | 19 ++++++++++---------
3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index 19a20ff420b7f..b8b9e7911e559 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -269,6 +269,7 @@ int mdev_device_create(struct mdev_type *type, const guid_t *uuid)
mdev->dev.parent = parent->dev;
mdev->dev.bus = &mdev_bus_type;
mdev->dev.release = mdev_device_release;
+ mdev->dev.groups = mdev_device_groups;
mdev->type = type;
/* Pairs with the put in mdev_device_release() */
kobject_get(&type->kobj);
diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
index 5a7ffd4e770fd..7c9fc79f3d838 100644
--- a/drivers/vfio/mdev/mdev_private.h
+++ b/drivers/vfio/mdev/mdev_private.h
@@ -32,6 +32,8 @@ struct mdev_type {
unsigned int type_group_id;
};

+extern const struct attribute_group *mdev_device_groups[];
+
#define to_mdev_type_attr(_attr) \
container_of(_attr, struct mdev_type_attribute, attr)
#define to_mdev_type(_kobj) \
diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c
index 5a3873d1a275a..0ccfeb3dda245 100644
--- a/drivers/vfio/mdev/mdev_sysfs.c
+++ b/drivers/vfio/mdev/mdev_sysfs.c
@@ -244,11 +244,20 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr,

static DEVICE_ATTR_WO(remove);

-static const struct attribute *mdev_device_attrs[] = {
+static struct attribute *mdev_device_attrs[] = {
&dev_attr_remove.attr,
NULL,
};

+static const struct attribute_group mdev_device_group = {
+ .attrs = mdev_device_attrs,
+};
+
+const struct attribute_group *mdev_device_groups[] = {
+ &mdev_device_group,
+ NULL
+};
+
int mdev_create_sysfs_files(struct mdev_device *mdev)
{
struct mdev_type *type = mdev->type;
@@ -262,15 +271,8 @@ int mdev_create_sysfs_files(struct mdev_device *mdev)
ret = sysfs_create_link(kobj, &type->kobj, "mdev_type");
if (ret)
goto type_link_failed;
-
- ret = sysfs_create_files(kobj, mdev_device_attrs);
- if (ret)
- goto create_files_failed;
-
return ret;

-create_files_failed:
- sysfs_remove_link(kobj, "mdev_type");
type_link_failed:
sysfs_remove_link(mdev->type->devices_kobj, dev_name(&mdev->dev));
return ret;
@@ -280,7 +282,6 @@ void mdev_remove_sysfs_files(struct mdev_device *mdev)
{
struct kobject *kobj = &mdev->dev.kobj;

- sysfs_remove_files(kobj, mdev_device_attrs);
sysfs_remove_link(kobj, "mdev_type");
sysfs_remove_link(mdev->type->devices_kobj, dev_name(&mdev->dev));
}
--
2.30.2