From patchwork Mon Apr 20 12:33:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tiezhu Yang X-Patchwork-Id: 11498819 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0383614B4 for ; Mon, 20 Apr 2020 12:34:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E885722202 for ; Mon, 20 Apr 2020 12:34:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726715AbgDTMeD (ORCPT ); Mon, 20 Apr 2020 08:34:03 -0400 Received: from mail.loongson.cn ([114.242.206.163]:52242 "EHLO loongson.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726615AbgDTMeC (ORCPT ); Mon, 20 Apr 2020 08:34:02 -0400 Received: from linux.localdomain (unknown [113.200.148.30]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9Dxb9uzlp1eHSgqAA--.29S5; Mon, 20 Apr 2020 20:33:59 +0800 (CST) From: Tiezhu Yang To: Luis Chamberlain , Shuah Khan , Andrew Morton , Jessica Yu Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Markus Elfring , Xuefeng Li Subject: [PATCH v3 3/4] kmod: Return directly if module name is empty in request_module() Date: Mon, 20 Apr 2020 20:33:54 +0800 Message-Id: <1587386035-5188-4-git-send-email-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1587386035-5188-1-git-send-email-yangtiezhu@loongson.cn> References: <1587386035-5188-1-git-send-email-yangtiezhu@loongson.cn> X-CM-TRANSID: AQAAf9Dxb9uzlp1eHSgqAA--.29S5 X-Coremail-Antispam: 1UD129KBjvJXoW7WFW8urWkur1fGry7XF45GFg_yoW8GFWxpF 45AFWFqr4ftw1qva97Jr95WFyYgrZrGrsxXFs5Crs3AF98trnFyrn8G3WYgrW5uF4Fgr1j yr4vvr15uryUuF7anT9S1TB71UUUUj7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUmS14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JrWl82xGYIkIc2 x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_Gr0_Xr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UM2 8EF7xvwVC2z280aVAFwI0_Cr1j6rxdM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAa w2AFwI0_JF0_Jw1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrV C2j2WlYx0E2Ix0cI8IcVAFwI0_JrI_JrylYx0Ex4A2jsIE14v26r4j6F4UMcvjeVCFs4IE 7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lc7CjxV Aaw2AFwI0_GFv_Wrylc2xSY4AK67AK6ryUMxAIw28IcxkI7VAKI48JMxC20s026xCaFVCj c4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4 CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1I6r4U MIIF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF 4lIxAIcVC2z280aVAFwI0_Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBI daVFxhVjvjDU0xZFpf9x0pRwqXdUUUUU= X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation. Call trace: request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL); sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256. Signed-off-by: Tiezhu Yang --- v3: - no changes v2: - update the commit message to explain the detailed reason kernel/kmod.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/kmod.c b/kernel/kmod.c index 3cd075c..5851444 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -28,6 +28,8 @@ #include +#define MODULE_NOT_FOUND 256 + /* * Assuming: * @@ -144,6 +146,9 @@ int __request_module(bool wait, const char *fmt, ...) if (ret >= MODULE_NAME_LEN) return -ENAMETOOLONG; + if (strlen(module_name) == 0) + return MODULE_NOT_FOUND; + ret = security_kernel_module_request(module_name); if (ret) return ret;