pstore: Drop useless try_module_get() for backend

There is no reason to be doing a module get/put in pstore_register(),
since the module calling pstore_register() cannot be unloaded since it
hasn't finished its initialization. Remove it so there is no confusion
about how registration ordering works.

Link: https://lore.kernel.org/lkml/20200506152114.50375-2-keescook@chromium.org/Signed-off-by: Kees Cook <keescook@chromium.org>

fs/pstore/platform.c

@@ -555,8 +555,6 @@ static int pstore_write_user_compat(struct pstore_record *record,
  */
 int pstore_register(struct pstore_info *psi)
 {
-	struct module *owner = psi->owner;
-
 	if (backend && strcmp(backend, psi->name)) {
 		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
 		return -EPERM;
@@ -591,10 +589,6 @@ int pstore_register(struct pstore_info *psi)
 	sema_init(&psinfo->buf_lock, 1);
 	spin_unlock(&pstore_lock);
 
-	if (owner && !try_module_get(owner)) {
-		psinfo = NULL;
-		return -EINVAL;
-	}
 
 	if (psi->flags & PSTORE_FLAGS_DMESG)
 		allocate_buf_for_compression();
@@ -626,8 +620,6 @@ int pstore_register(struct pstore_info *psi)
 
 	pr_info("Registered %s as persistent store backend\n", psi->name);
 
-	module_put(owner);
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pstore_register);