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

Mimi Zohar
2018-05-29T18:02:21Z

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>
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