On Tue, 27 Aug 2019 14:16:50 -0500
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
>
> ---
> Changelog:
>
> v0->v1:
> - Moved alias length check outside of the parent lock
> - Moved alias and digest allocation from kvzalloc to kzalloc
> - [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| 110 ++-
> drivers/vfio/mdev/mdev_private.h | 5 +-
> drivers/vfio/mdev/mdev_sysfs.c | 13 ++--
> include/linux/mdev.h | 4 ++
> 4 files changed, 122 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index b558d4cfd082..62d29f57fe0c 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -10,9 +10,11 @@
> #include
> #include
> #include
> +#include
> #include
> #include
> #include
> +#include
>
> #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(_list_lock);
>
> dev_dbg(>dev, "MDEV: destroying\n");
> + kfree(mdev->alias);
> kfree(mdev);
> }
>
> @@ -269,18 +284,88 @@ 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 = 0;
> +
> + /*
> + * 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);
> + if (!alias)
> + return NULL;
> +
> + /* Allocate and init descriptor */
> + hash_desc = kvzalloc(sizeof(*hash_desc) +
> + crypto_shash_descsize(alias_hash),
> + GFP_KERNEL);
> + if (!hash_desc)
> + 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;
> + }
> + crypto_shash_init(hash_desc);
> + crypto_shash_update(hash_desc, uuid, UUID_STRING_LEN);
> + crypto_shash_final(hash_desc, digest);
All of these can fail and many, if not most, of the callers appear
that they might test the return value. Thanks,
Alex
> + bin2hex(alias, digest, min_t(unsigned int, digest_size, alias_len / 2));
> + /*
> + * When alias length is odd, zero out and additional last byte
> + * that bin2hex has copied.
> + */
> + if (max_alias_len % 2)
> + alias[max_alias_len] = 0;
> +
> + kfree(digest);
> + kvfree(hash_desc);
> + return alias;
> +
> +digest_err:
> + kvfree(hash_desc);
> +desc_err:
> + kfree(alias);
> + return NULL;
> +}
> +
> +int mdev_device_create(struct kobject *kobj, struct device *dev,
> +const char *uuid_str, const guid_t *uuid)
> {
>
