Re: [PATCH v4 1/8] security: define new LSM hook named security_kernel_load_data

Serge E. Hallyn
2018-06-04T19:59:54Z

Quoting Mimi Zohar (zohar@linux.vnet.ibm.com):
> 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.
>
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Acked-by: Serge Hallyn <serge@hallyn.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>
>
> 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 | 33 +++++++++++++++++++++++++++++++++
> security/security.c | 5 +++++
> 3 files changed, 44 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..3d54d5945755 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -159,6 +159,33 @@ 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);
>
> +
> +#define __kernel_load_data_id(id) \
> + id(UNKNOWN, unknown) \
> + id(FIRMWARE, firmware) \
> + id(MODULE, kernel-module) \
> + id(KEXEC_IMAGE, kexec-image) \
> + id(MAX_ID, )
> +
> +#define __data_id_enumify(ENUM, dummy) LOADING_ ## ENUM,
> +#define __data_id_stringify(dummy, str) #str,
> +
> +enum kernel_load_data_id {
> + __kernel_load_data_id(__data_id_enumify)
> +};
> +
> +static const char * const kernel_load_data_str[] = {
> + __kernel_load_data_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 +347,7 @@ 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 +937,11 @@ 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 68f46d849abe..c2de2f134854 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1056,6 +1056,11 @@ 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)
> {
> --
> 2.7.5