SELinux: add selinux_kernel_module_request

This patch adds a new selinux hook so SELinux can arbitrate if a given
process should be allowed to trigger a request for the kernel to try to
load a module.  This is a different operation than a process trying to load
a module itself, which is already protected by CAP_SYS_MODULE.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/hooks.c

@@ -3296,6 +3296,11 @@ static int selinux_kernel_create_files_as(struct cred *new, struct inode *inode)
 	return 0;
 }
 
+static int selinux_kernel_module_request(void)
+{
+	return task_has_system(current, SYSTEM__MODULE_REQUEST);
+}
+
 static int selinux_task_setpgid(struct task_struct *p, pid_t pgid)
 {
 	return current_has_perm(p, PROCESS__SETPGID);
@@ -5404,6 +5409,7 @@ static struct security_operations selinux_ops = {
 	.cred_prepare =			selinux_cred_prepare,
 	.kernel_act_as =		selinux_kernel_act_as,
 	.kernel_create_files_as =	selinux_kernel_create_files_as,
+	.kernel_module_request =	selinux_kernel_module_request,
 	.task_setpgid =			selinux_task_setpgid,
 	.task_getpgid =			selinux_task_getpgid,
 	.task_getsid =			selinux_task_getsid,

security/selinux/include/av_perm_to_string.h

@@ -107,6 +107,7 @@
    S_(SECCLASS_SYSTEM, SYSTEM__SYSLOG_READ, "syslog_read")
    S_(SECCLASS_SYSTEM, SYSTEM__SYSLOG_MOD, "syslog_mod")
    S_(SECCLASS_SYSTEM, SYSTEM__SYSLOG_CONSOLE, "syslog_console")
+   S_(SECCLASS_SYSTEM, SYSTEM__MODULE_REQUEST, "module_request")
    S_(SECCLASS_CAPABILITY, CAPABILITY__CHOWN, "chown")
    S_(SECCLASS_CAPABILITY, CAPABILITY__DAC_OVERRIDE, "dac_override")
    S_(SECCLASS_CAPABILITY, CAPABILITY__DAC_READ_SEARCH, "dac_read_search")

security/selinux/include/av_permissions.h

@@ -508,6 +508,7 @@
 #define SYSTEM__SYSLOG_READ                       0x00000002UL
 #define SYSTEM__SYSLOG_MOD                        0x00000004UL
 #define SYSTEM__SYSLOG_CONSOLE                    0x00000008UL
+#define SYSTEM__MODULE_REQUEST                    0x00000010UL
 #define CAPABILITY__CHOWN                         0x00000001UL
 #define CAPABILITY__DAC_OVERRIDE                  0x00000002UL
 #define CAPABILITY__DAC_READ_SEARCH               0x00000004UL