Re: [PATCH v5 02/12] libnvdimm: create keyring to store security keys

[Eric Biggers <ebiggers3@gmail.com>]

Just a few superficial comments:

On Tue, Jul 17, 2018 at 01:54:15PM -0700, Dave Jiang wrote:
> Prepping the libnvdimm to support security management by adding a keyring
> in order to provide passphrase management through the kernel key management
> APIs.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/nvdimm/core.c      |    7 +++
>  drivers/nvdimm/dimm_devs.c |   96 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/nvdimm/nd-core.h   |    1 
>  include/linux/libnvdimm.h  |    5 ++
>  4 files changed, 107 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c
> index acce050856a8..3cd33d5c7cf0 100644
> --- a/drivers/nvdimm/core.c
> +++ b/drivers/nvdimm/core.c
> @@ -437,9 +437,12 @@ static __init int libnvdimm_init(void)
>  {
>  	int rc;
>  
> -	rc = nvdimm_bus_init();
> +	rc = nvdimm_devs_init();
>  	if (rc)
>  		return rc;
> +	rc = nvdimm_bus_init();
> +	if (rc)
> +		goto err_bus;
>  	rc = nvdimm_init();
>  	if (rc)
>  		goto err_dimm;
> @@ -454,6 +457,8 @@ static __init int libnvdimm_init(void)
>  	nvdimm_exit();
>   err_dimm:
>  	nvdimm_bus_exit();
> + err_bus:
> +	nvdimm_devs_exit();
>  	return rc;
>  }
>  
> diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
> index 8d348b22ba45..1dcbb653455b 100644
> --- a/drivers/nvdimm/dimm_devs.c
> +++ b/drivers/nvdimm/dimm_devs.c
> @@ -18,12 +18,54 @@
>  #include <linux/io.h>
>  #include <linux/fs.h>
>  #include <linux/mm.h>
> +#include <linux/cred.h>
> +#include <keys/user-type.h>
> +#include <linux/key-type.h>
> +#include <linux/keyctl.h>
>  #include "nd-core.h"
>  #include "label.h"
>  #include "pmem.h"
>  #include "nd.h"
>  
>  static DEFINE_IDA(dimm_ida);
> +static const struct cred *nvdimm_cred;
> +
> +static int nvdimm_key_instantiate(struct key *key,
> +		struct key_preparsed_payload *prep);
> +static void nvdimm_key_destroy(struct key *key);
> +
> +struct key_type nvdimm_key_type = {
> +	.name = "nvdimm",
> +	.instantiate = nvdimm_key_instantiate,
> +	.destroy = nvdimm_key_destroy,
> +	.describe = user_describe,
> +	/*
> +	 * The reason to have default data length to be len*2 is to
> +	 * accomodate the payload when we are doing a key change where
> +	 * the we stuff the old key and new key in the same payload.
> +	 */
> +	.def_datalen = NVDIMM_PASSPHRASE_LEN * 2,
> +};
> +
> +static int nvdimm_key_instantiate(struct key *key,
> +		struct key_preparsed_payload *prep)
> +{
> +	char *payload;
> +
> +	payload = kzalloc(nvdimm_key_type.def_datalen, GFP_KERNEL);
> +	if (!payload)
> +		return -ENOMEM;
> +
> +	key->datalen = min(nvdimm_key_type.def_datalen, prep->datalen);
> +	memcpy(payload, prep->data, key->datalen);
> +	key->payload.data[0] = payload;
> +	return 0;
> +}

This should return an error code if the user provided a too long payload, rather
than silently truncating it.

> +
> +static void nvdimm_key_destroy(struct key *key)
> +{
> +	kfree(key->payload.data[0]);
> +}

kzfree()

> -void __exit nvdimm_devs_exit(void)
> +static int nvdimm_register_keyring(void)
> +{
> +	struct cred *cred;
> +	struct key *keyring;
> +	int rc;
> +
> +	rc = register_key_type(&nvdimm_key_type);
> +	if (rc < 0)
> +		return rc;
> +
> +	cred = prepare_kernel_cred(NULL);
> +	if (!cred) {
> +		rc = -ENOMEM;
> +		goto failed_cred;
> +	}
> +
> +	keyring = keyring_alloc(".nvdimm",
> +			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
> +			(KEY_POS_ALL & ~KEY_POS_SETATTR) |
> +			(KEY_USR_ALL & ~KEY_USR_SETATTR),
> +			KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
> +	if (IS_ERR(keyring)) {
> +		rc = PTR_ERR(keyring);
> +		goto failed_keyring;
> +	}
> +
> +	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
> +	cred->thread_keyring = keyring;
> +	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
> +	nvdimm_cred = cred;
> +	return 0;
> +
> + failed_cred:
> +	unregister_key_type(&nvdimm_key_type);
> + failed_keyring:
> +	put_cred(cred);
> +	return rc;
> +}

The labels here are backwards.  It should be

failed_keyring:
	put_cred(cred);
failed_cred:
	unregister_key_type(&nvdimm_key_type);
	return rc;

> +
> +static void nvdimm_unregister_keyring(void)
> +{
> +	key_revoke(nvdimm_cred->thread_keyring);
> +	unregister_key_type(&nvdimm_key_type);
> +	put_cred(nvdimm_cred);
> +}
> +
> +int __init nvdimm_devs_init(void)
> +{
> +	return nvdimm_register_keyring();
> +}
> +
> +void  nvdimm_devs_exit(void)
>  {
> +	nvdimm_unregister_keyring();
>  	ida_destroy(&dimm_ida);
>  }
> diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
> index 79274ead54fb..2af0f89c4010 100644
> --- a/drivers/nvdimm/nd-core.h
> +++ b/drivers/nvdimm/nd-core.h
> @@ -76,6 +76,7 @@ static inline bool is_memory(struct device *dev)
>  struct nvdimm_bus *walk_to_nvdimm_bus(struct device *nd_dev);
>  int __init nvdimm_bus_init(void);
>  void nvdimm_bus_exit(void);
> +int nvdimm_devs_init(void);
>  void nvdimm_devs_exit(void);
>  void nd_region_devs_exit(void);
>  void nd_region_probe_success(struct nvdimm_bus *nvdimm_bus, struct device *dev);
> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
> index 472171af7f60..09dd06f96f95 100644
> --- a/include/linux/libnvdimm.h
> +++ b/include/linux/libnvdimm.h
> @@ -155,6 +155,11 @@ static inline struct nd_blk_region_desc *to_blk_region_desc(
>  
>  }
>  
> +extern struct key_type nvdimm_key_type;
> +
> +#define NVDIMM_PASSPHRASE_LEN		32
> +#define NVDIMM_KEY_DESC_LEN		25
> +
>  void badrange_init(struct badrange *badrange);
>  int badrange_add(struct badrange *badrange, u64 addr, u64 length);
>  void badrange_forget(struct badrange *badrange, phys_addr_t start,
> 
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