security: define new LSM hook named security_kernel_load_data

Differentiate between the kernel reading a file specified by userspace
from the kernel loading a buffer containing 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: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>

3 files changed, 38 insertions, 0 deletions

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 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)
 {