Re: [PATCH v5 1/8] security: define new LSM hook named security_kernel_load_data

[J Freyensee <why2jjj.linux@gmail.com>]

On 7/2/18 7:37 AM, Mimi Zohar wrote:
> Differentiate between the kernel reading a file from the kernel loading
> data provided by userspace.  This patch defines a new LSM hook named
> security_kernel_load_data.

If this patch series is re-done, can we tweak the description here 
please?  From what I understood of the code in this patch, I'd tweak it as:

"Differentiate between the kernel reading a file specified by userspace 
and the kernel loading a block of data provided by userspace.  This 
patch defines a new LSM hook named security_kernel_load_data()."

 From the description, I got a tad confused if the the kernel reading a file was also provided by userspace (I know it may be 2nd-nature to people on this list, I'm still learning this kernel module).

Thanks,
Jay

> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> Cc: Eric Biederman <ebiederm@xmission.com>
> Cc: Luis R. Rodriguez <mcgrof@kernel.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Casey Schaufler <casey@schaufler-ca.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
>
> ---
> Changelog v5:
> - Share the kernel_load_data_id and kernel_read_file_id values,
> simplifying Loadpin's and other LSMs calling one LSM hook from the
> other.
>
> Changelog v4:
> - Define new LSM hook named security_kernel_load_data.
>
> Changelog v3:
> - Rename security_kernel_read_file to security_kernel_read_data().
>
> Changelog v2:
> - Define a generic wrapper named security_kernel_read_blob() for
> security_kernel_read_file().
>
> Changelog v1:
> - Define and call security_kexec_load(), a wrapper for
> security_kernel_read_file().
>
>   include/linux/lsm_hooks.h |  6 ++++++
>   include/linux/security.h  | 27 +++++++++++++++++++++++++++
>   security/security.c       |  5 +++++
>   3 files changed, 38 insertions(+)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 8f1131c8dd54..a08bc2587b96 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -576,6 +576,10 @@
>    *	userspace to load a kernel module with the given name.
>    *	@kmod_name name of the module requested by the kernel
>    *	Return 0 if successful.
> + * @kernel_load_data:
> + *	Load data provided by userspace.
> + *	@id kernel load data identifier
> + *	Return 0 if permission is granted.
>    * @kernel_read_file:
>    *	Read a file specified by userspace.
>    *	@file contains the file structure pointing to the file being read
> @@ -1582,6 +1586,7 @@ union security_list_options {
>   	int (*kernel_act_as)(struct cred *new, u32 secid);
>   	int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
>   	int (*kernel_module_request)(char *kmod_name);
> +	int (*kernel_load_data)(enum kernel_load_data_id id);
>   	int (*kernel_read_file)(struct file *file, enum kernel_read_file_id id);
>   	int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size,
>   				     enum kernel_read_file_id id);
> @@ -1872,6 +1877,7 @@ struct security_hook_heads {
>   	struct hlist_head cred_getsecid;
>   	struct hlist_head kernel_act_as;
>   	struct hlist_head kernel_create_files_as;
> +	struct hlist_head kernel_load_data;
>   	struct hlist_head kernel_read_file;
>   	struct hlist_head kernel_post_read_file;
>   	struct hlist_head kernel_module_request;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 63030c85ee19..3410acfe139c 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -159,6 +159,27 @@ extern int mmap_min_addr_handler(struct ctl_table *table, int write,
>   typedef int (*initxattrs) (struct inode *inode,
>   			   const struct xattr *xattr_array, void *fs_data);
>   
> +
> +/* Keep the kernel_load_data_id enum in sync with kernel_read_file_id */
> +#define __data_id_enumify(ENUM, dummy) LOADING_ ## ENUM,
> +#define __data_id_stringify(dummy, str) #str,
> +
> +enum kernel_load_data_id {
> +	__kernel_read_file_id(__data_id_enumify)
> +};
> +
> +static const char * const kernel_load_data_str[] = {
> +	__kernel_read_file_id(__data_id_stringify)
> +};
> +
> +static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id)
> +{
> +	if ((unsigned)id >= LOADING_MAX_ID)
> +		return kernel_load_data_str[LOADING_UNKNOWN];
> +
> +	return kernel_load_data_str[id];
> +}
> +
>   #ifdef CONFIG_SECURITY
>   
>   struct security_mnt_opts {
> @@ -320,6 +341,7 @@ void security_cred_getsecid(const struct cred *c, u32 *secid);
>   int security_kernel_act_as(struct cred *new, u32 secid);
>   int security_kernel_create_files_as(struct cred *new, struct inode *inode);
>   int security_kernel_module_request(char *kmod_name);
> +int security_kernel_load_data(enum kernel_load_data_id id);
>   int security_kernel_read_file(struct file *file, enum kernel_read_file_id id);
>   int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
>   				   enum kernel_read_file_id id);
> @@ -909,6 +931,11 @@ static inline int security_kernel_module_request(char *kmod_name)
>   	return 0;
>   }
>   
> +static inline int security_kernel_load_data(enum kernel_load_data_id id)
> +{
> +	return 0;
> +}
> +
>   static inline int security_kernel_read_file(struct file *file,
>   					    enum kernel_read_file_id id)
>   {
> diff --git a/security/security.c b/security/security.c
> index e7d76a8000a5..05fe5b1932d7 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1061,6 +1061,11 @@ int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
>   }
>   EXPORT_SYMBOL_GPL(security_kernel_post_read_file);
>   
> +int security_kernel_load_data(enum kernel_load_data_id id)
> +{
> +	return call_int_hook(kernel_load_data, 0, id);
> +}
> +
>   int security_task_fix_setuid(struct cred *new, const struct cred *old,
>   			     int flags)
>   {