security: introduce kernel_module_from_file hook

Now that kernel module origins can be reasoned about, provide a hook to
the LSMs to make policy decisions about the module file. This will let
Chrome OS enforce that loadable kernel modules can only come from its
read-only hash-verified root filesystem. Other LSMs can, for example,
read extended attributes for signatures, etc.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 11 insertions, 0 deletions

diff --git a/security/capability.c b/security/capability.c
index b14a30c234b8..0fe5a026aef8 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -395,6 +395,11 @@ static int cap_kernel_module_request(char *kmod_name)
         return 0;
 }
 
+static int cap_kernel_module_from_file(struct file *file)
+{
+        return 0;
+}
+
 static int cap_task_setpgid(struct task_struct *p, pid_t pgid)
 {
         return 0;
@@ -967,6 +972,7 @@ void __init security_fixup_ops(struct security_operations *ops)
         set_to_cap_if_null(ops, kernel_act_as);
         set_to_cap_if_null(ops, kernel_create_files_as);
         set_to_cap_if_null(ops, kernel_module_request);
+        set_to_cap_if_null(ops, kernel_module_from_file);
         set_to_cap_if_null(ops, task_fix_setuid);
         set_to_cap_if_null(ops, task_setpgid);
         set_to_cap_if_null(ops, task_getpgid);
diff --git a/security/security.c b/security/security.c
index 8dcd4ae10a5f..ce88630de15d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -820,6 +820,11 @@ int security_kernel_module_request(char *kmod_name)
         return security_ops->kernel_module_request(kmod_name);
 }
 
+int security_kernel_module_from_file(struct file *file)
+{
+        return security_ops->kernel_module_from_file(file);
+}
+
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
                              int flags)
 {