security: introducing security_request_module

Calling request_module() will trigger a userspace upcall which will load a
new module into the kernel.  This can be a dangerous event if the process
able to trigger request_module() is able to control either the modprobe
binary or the module binary.  This patch adds a new security hook to
request_module() which can be used by an LSM to control a processes ability
to call request_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>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index 57ead99d2593..1e3dd86eea99 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -678,6 +678,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *      @inode points to the inode to use as a reference.
  *      The current task must be the one that nominated @inode.
  *      Return 0 if successful.
+ * @kernel_module_request:
+ *      Ability to trigger the kernel to automatically upcall to userspace for
+ *      userspace to load a kernel module with the given name.
  * @task_setuid:
  *      Check permission before setting one or more of the user identity
  *      attributes of the current process.  The @flags parameter indicates
@@ -1489,6 +1492,7 @@ struct security_operations {
         void (*cred_commit)(struct cred *new, const struct cred *old);
         int (*kernel_act_as)(struct cred *new, u32 secid);
         int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
+        int (*kernel_module_request)(void);
         int (*task_setuid) (uid_t id0, uid_t id1, uid_t id2, int flags);
         int (*task_fix_setuid) (struct cred *new, const struct cred *old,
                                 int flags);
@@ -1741,6 +1745,7 @@ int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
 void security_commit_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(void);
 int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags);
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
                              int flags);
@@ -2292,6 +2297,11 @@ static inline int security_kernel_create_files_as(struct cred *cred,
         return 0;
 }
 
+static inline int security_kernel_module_request(void)
+{
+        return 0;
+}
+
 static inline int security_task_setuid(uid_t id0, uid_t id1, uid_t id2,
                                        int flags)
 {