On 2019/8/29 19:18, Parav Pandit wrote: > Some vendor drivers want an identifier for an mdev device that is > shorter than the UUID, due to length restrictions in the consumers of > that identifier. > > Add a callback that allows a vendor driver to request an alias of a > specified length to be generated for an mdev device. If generated, > that alias is checked for collisions. > > It is an optional attribute. > mdev alias is generated using sha1 from the mdev name. > > Signed-off-by: Parav Pandit <pa...@mellanox.com> > > --- > Changelog: > v1->v2: > - Kept mdev_device naturally aligned > - Added error checking for crypt_*() calls > - Corrected a typo from 'and' to 'an' > - Changed return type of generate_alias() from int to char* > v0->v1: > - Moved alias length check outside of the parent lock > - Moved alias and digest allocation from kvzalloc to kzalloc > - &alias[0] changed to alias > - alias_length check is nested under get_alias_length callback check > - Changed comments to start with an empty line > - Fixed cleaunup of hash if mdev_bus_register() fails > - Added comment where alias memory ownership is handed over to mdev device > - Updated commit log to indicate motivation for this feature > --- > drivers/vfio/mdev/mdev_core.c | 123 ++++++++++++++++++++++++++++++- > drivers/vfio/mdev/mdev_private.h | 5 +- > drivers/vfio/mdev/mdev_sysfs.c | 13 ++-- > include/linux/mdev.h | 4 + > 4 files changed, 135 insertions(+), 10 deletions(-) > > diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c > index b558d4cfd082..3bdff0469607 100644 > --- a/drivers/vfio/mdev/mdev_core.c > +++ b/drivers/vfio/mdev/mdev_core.c > @@ -10,9 +10,11 @@ > #include <linux/module.h> > #include <linux/device.h> > #include <linux/slab.h> > +#include <linux/mm.h> > #include <linux/uuid.h> > #include <linux/sysfs.h> > #include <linux/mdev.h> > +#include <crypto/hash.h> > > #include "mdev_private.h" > > @@ -27,6 +29,8 @@ static struct class_compat *mdev_bus_compat_class; > static LIST_HEAD(mdev_list); > static DEFINE_MUTEX(mdev_list_lock); > > +static struct crypto_shash *alias_hash; > + > struct device *mdev_parent_dev(struct mdev_device *mdev) > { > return mdev->parent->dev; > @@ -150,6 +154,16 @@ int mdev_register_device(struct device *dev, const > struct mdev_parent_ops *ops) > if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups) > return -EINVAL; > > + if (ops->get_alias_length) { > + unsigned int digest_size; > + unsigned int aligned_len; > + > + aligned_len = roundup(ops->get_alias_length(), 2); > + digest_size = crypto_shash_digestsize(alias_hash); > + if (aligned_len / 2 > digest_size) > + return -EINVAL; > + } > + > dev = get_device(dev); > if (!dev) > return -EINVAL; > @@ -259,6 +273,7 @@ static void mdev_device_free(struct mdev_device *mdev) > mutex_unlock(&mdev_list_lock); > > dev_dbg(&mdev->dev, "MDEV: destroying\n"); > + kfree(mdev->alias); > kfree(mdev); > } > > @@ -269,18 +284,101 @@ static void mdev_device_release(struct device *dev) > mdev_device_free(mdev); > } > > -int mdev_device_create(struct kobject *kobj, > - struct device *dev, const guid_t *uuid) > +static const char * > +generate_alias(const char *uuid, unsigned int max_alias_len) > +{ > + struct shash_desc *hash_desc; > + unsigned int digest_size; > + unsigned char *digest; > + unsigned int alias_len; > + char *alias; > + int ret; > + > + /* > + * Align to multiple of 2 as bin2hex will generate > + * even number of bytes. > + */ > + alias_len = roundup(max_alias_len, 2); > + alias = kzalloc(alias_len + 1, GFP_KERNEL);
It seems the mtty_alias_length in mtty.c can be set from module parameter, and user can set a very large number, maybe limit the max of the alias_len before calling kzalloc? > + if (!alias) > + return ERR_PTR(-ENOMEM); > + > + /* Allocate and init descriptor */ > + hash_desc = kvzalloc(sizeof(*hash_desc) + > + crypto_shash_descsize(alias_hash), > + GFP_KERNEL); > + if (!hash_desc) { > + ret = -ENOMEM; > + goto desc_err; > + } > + > + hash_desc->tfm = alias_hash; > + > + digest_size = crypto_shash_digestsize(alias_hash); > + > + digest = kzalloc(digest_size, GFP_KERNEL); > + if (!digest) { > + ret = -ENOMEM; > + goto digest_err; > + } > + ret = crypto_shash_init(hash_desc); > + if (ret) > + goto hash_err; > + > + ret = crypto_shash_update(hash_desc, uuid, UUID_STRING_LEN); > + if (ret) > + goto hash_err; > + > + ret = crypto_shash_final(hash_desc, digest); > + if (ret) > + goto hash_err; > + > + bin2hex(alias, digest, min_t(unsigned int, digest_size, alias_len / 2)); > + /* > + * When alias length is odd, zero out an additional last byte > + * that bin2hex has copied. > + */ > + if (max_alias_len % 2) > + alias[max_alias_len] = 0; > + > + kfree(digest); > + kvfree(hash_desc); > + return alias; > + > +hash_err: > + kfree(digest); > +digest_err: > + kvfree(hash_desc); > +desc_err: > + kfree(alias); > + return ERR_PTR(ret); > +} > + > +int mdev_device_create(struct kobject *kobj, struct device *dev, > + const char *uuid_str, const guid_t *uuid) > { > int ret; > struct mdev_device *mdev, *tmp; > struct mdev_parent *parent; > struct mdev_type *type = to_mdev_type(kobj); > + const char *alias = NULL; > > parent = mdev_get_parent(type->parent); > if (!parent) > return -EINVAL; > > + if (parent->ops->get_alias_length) { > + unsigned int alias_len; > + > + alias_len = parent->ops->get_alias_length(); > + if (alias_len) { > + alias = generate_alias(uuid_str, alias_len); > + if (IS_ERR(alias)) { > + ret = PTR_ERR(alias); > + goto alias_fail; > + } > + } > + } > mutex_lock(&mdev_list_lock); > > /* Check for duplicate */ > @@ -300,6 +398,12 @@ int mdev_device_create(struct kobject *kobj, > } > > guid_copy(&mdev->uuid, uuid); > + mdev->alias = alias; > + /* > + * At this point alias memory is owned by the mdev. > + * Mark it NULL, so that only mdev can free it. > + */ > + alias = NULL; > list_add(&mdev->next, &mdev_list); > mutex_unlock(&mdev_list_lock); > > @@ -346,6 +450,8 @@ int mdev_device_create(struct kobject *kobj, > up_read(&parent->unreg_sem); > put_device(&mdev->dev); > mdev_fail: > + kfree(alias); > +alias_fail: > mdev_put_parent(parent); > return ret; > } > @@ -406,7 +512,17 @@ EXPORT_SYMBOL(mdev_get_iommu_device); > > static int __init mdev_init(void) > { > - return mdev_bus_register(); > + int ret; > + > + alias_hash = crypto_alloc_shash("sha1", 0, 0); > + if (!alias_hash) > + return -ENOMEM; > + > + ret = mdev_bus_register(); > + if (ret) > + crypto_free_shash(alias_hash); > + > + return ret; > } > > static void __exit mdev_exit(void) > @@ -415,6 +531,7 @@ static void __exit mdev_exit(void) > class_compat_unregister(mdev_bus_compat_class); > > mdev_bus_unregister(); > + crypto_free_shash(alias_hash); > } > > module_init(mdev_init) > diff --git a/drivers/vfio/mdev/mdev_private.h > b/drivers/vfio/mdev/mdev_private.h > index 7d922950caaf..078fdaf7836e 100644 > --- a/drivers/vfio/mdev/mdev_private.h > +++ b/drivers/vfio/mdev/mdev_private.h > @@ -32,6 +32,7 @@ struct mdev_device { > struct list_head next; > struct kobject *type_kobj; > struct device *iommu_device; > + const char *alias; > bool active; > }; > > @@ -57,8 +58,8 @@ void parent_remove_sysfs_files(struct mdev_parent *parent); > int mdev_create_sysfs_files(struct device *dev, struct mdev_type *type); > void mdev_remove_sysfs_files(struct device *dev, struct mdev_type *type); > > -int mdev_device_create(struct kobject *kobj, > - struct device *dev, const guid_t *uuid); > +int mdev_device_create(struct kobject *kobj, struct device *dev, > + const char *uuid_str, const guid_t *uuid); > int mdev_device_remove(struct device *dev); > > #endif /* MDEV_PRIVATE_H */ > diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c > index 7570c7602ab4..43afe0e80b76 100644 > --- a/drivers/vfio/mdev/mdev_sysfs.c > +++ b/drivers/vfio/mdev/mdev_sysfs.c > @@ -63,15 +63,18 @@ static ssize_t create_store(struct kobject *kobj, struct > device *dev, > return -ENOMEM; > > ret = guid_parse(str, &uuid); > - kfree(str); > if (ret) > - return ret; > + goto err; > > - ret = mdev_device_create(kobj, dev, &uuid); > + ret = mdev_device_create(kobj, dev, str, &uuid); > if (ret) > - return ret; > + goto err; > > - return count; > + ret = count; > + > +err: > + kfree(str); > + return ret; > } > > MDEV_TYPE_ATTR_WO(create); > diff --git a/include/linux/mdev.h b/include/linux/mdev.h > index 0ce30ca78db0..f036fe9854ee 100644 > --- a/include/linux/mdev.h > +++ b/include/linux/mdev.h > @@ -72,6 +72,9 @@ struct device *mdev_get_iommu_device(struct device *dev); > * @mmap: mmap callback > * @mdev: mediated device structure > * @vma: vma structure > + * @get_alias_length: Generate alias for the mdevs of this parent > based on the > + * mdev device name when it returns non zero alias length. > + * It is optional. > * Parent device that support mediated device should be registered with mdev > * module with mdev_parent_ops structure. > **/ > @@ -92,6 +95,7 @@ struct mdev_parent_ops { > long (*ioctl)(struct mdev_device *mdev, unsigned int cmd, > unsigned long arg); > int (*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma); > + unsigned int (*get_alias_length)(void); > }; > > /* interface for exporting mdev supported type attributes */ >