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>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index 05e88bdcf7d9..0f6afc657f77 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -694,6 +694,12 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *      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_module_from_file:
+ *      Load a kernel module from userspace.
+ *      @file contains the file structure pointing to the file containing
+ *      the kernel module to load. If the module is being loaded from a blob,
+ *      this argument will be NULL.
+ *      Return 0 if permission is granted.
  * @task_fix_setuid:
  *      Update the module's state after setting one or more of the user
  *      identity attributes of the current process.  The @flags parameter
@@ -1508,6 +1514,7 @@ struct security_operations {
         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_module_from_file)(struct file *file);
         int (*task_fix_setuid) (struct cred *new, const struct cred *old,
                                 int flags);
         int (*task_setpgid) (struct task_struct *p, pid_t pgid);
@@ -1765,6 +1772,7 @@ void security_transfer_creds(struct cred *new, const struct cred *old);
 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_module_from_file(struct file *file);
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
                              int flags);
 int security_task_setpgid(struct task_struct *p, pid_t pgid);
@@ -2278,6 +2286,11 @@ static inline int security_kernel_module_request(char *kmod_name)
         return 0;
 }
 
+static inline int security_kernel_module_from_file(struct file *file)
+{
+        return 0;
+}
+
 static inline int security_task_fix_setuid(struct cred *new,
                                            const struct cred *old,
                                            int flags)