[RFC PATCH 2/2] dm-crypt: Use any key type which is registered

[Maik Otto]

Hi

little bug fix, because this version chrashed with access violation
on an i.MX6Quad with a Mainline Kernel 4.19.88

> There was only 2 key_type supported by dm-crypt which limits other
> implementations.
>
> This patch allows to use any key_type which is registered obtaining
> the key_type from key framework.
>
> This also remove the compilation dependency between dm-crypt and
> key implementations.
>
> Signed-off-by: Franck LENORMAND <franck.lenormand at nxp.com>
> ---
>   drivers/md/dm-crypt.c    | 11 ++++++-----
>   include/linux/key-type.h |  2 ++
>   security/keys/key.c      | 42 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 50 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index dd538e6..e25efc2 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -35,6 +35,7 @@
>   #include <crypto/authenc.h>
>   #include <linux/rtnetlink.h> /* for struct rtattr and RTA macros only */
>   #include <keys/user-type.h>
> +#include <linux/key-type.h>
>   
>   #include <linux/device-mapper.h>
>   
> @@ -2010,6 +2011,7 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string
>   	int ret;
>   	struct key *key;
>   	const struct user_key_payload *ukp;
> +	struct key_type *type;
>   
>   	/*
>   	 * Reject key_string with whitespace. dm core currently lacks code for
> @@ -2025,16 +2027,15 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string
>   	if (!key_desc || key_desc == key_string || !strlen(key_desc + 1))
>   		return -EINVAL;
>   
> -	if (strncmp(key_string, "logon:", key_desc - key_string + 1) &&
> -	    strncmp(key_string, "user:", key_desc - key_string + 1))
> -		return -EINVAL;
> +	type = get_key_type(key_string, key_desc - key_string);
> +	if (!type)
> +		return -ENOENT;
>   
>   	new_key_string = kstrdup(key_string, GFP_KERNEL);
>   	if (!new_key_string)
>   		return -ENOMEM;
>   
> -	key = request_key(key_string[0] == 'l' ? &key_type_logon : &key_type_user,
> -			  key_desc + 1, NULL);
> +	key = request_key(type, key_desc + 1, NULL);
>   	if (IS_ERR(key)) {
>   		kzfree(new_key_string);
>   		return PTR_ERR(key);
> diff --git a/include/linux/key-type.h b/include/linux/key-type.h
> index bc9af55..2b2167b 100644
> --- a/include/linux/key-type.h
> +++ b/include/linux/key-type.h
> @@ -176,6 +176,8 @@ extern struct key_type key_type_keyring;
>   extern int register_key_type(struct key_type *ktype);
>   extern void unregister_key_type(struct key_type *ktype);
>   
> +extern struct key_type *get_key_type(const char *type_name, size_t string_size);
> +
>   extern int key_payload_reserve(struct key *key, size_t datalen);
>   extern int key_instantiate_and_link(struct key *key,
>   				    const void *data,
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 44a80d6..ef76114 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -1156,6 +1156,48 @@ void unregister_key_type(struct key_type *ktype)
>   }
>   EXPORT_SYMBOL(unregister_key_type);
>   
> +/**
> + * get_key_type - Get the type of key using its name
> + * @type_name: Name of the key type to get
> + * @string_size: Size of the string to match
> + *
> + * The functions support null ended string (string_size == 0) as well as
> + * pointer on a string matching a number of characters (string_size > 0)
> + *
> + * Returns a pointer on the key type if successful, -ENOENT if the key type
> + * is not registered.
> + */
> +struct key_type *get_key_type(const char *type_name, size_t string_size)
> +{
> +	struct key_type *p;
> +	struct key_type *ktype = ERR_PTR(-ENOENT);
> +
> +	if (!type_name)
> +		return ktype;
> +
> +	down_write(&key_types_sem);

down_write(&key_types_sem);  changed to down_read(&key_types_sem);

> +
> +	/* Search the key type in the list */
> +	list_for_each_entry(p, &key_types_list, link) {
> +		if (string_size) {
> +			if (strncmp(p->name, type_name, string_size) == 0) {
> +				ktype = p;
> +				break;
> +			}
> +		} else {
> +			if (strcmp(p->name, type_name) == 0) {
> +				ktype = p;
> +				break;
> +			}
> +		}
> +	}
> +
> +	up_read(&key_types_sem);
> +
> +	return ktype;
> +}
> +EXPORT_SYMBOL(get_key_type);
> +
>   /*
>    * Initialise the key management state.
>    */
>