From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93661C77B7A for ; Wed, 17 May 2023 10:21:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229542AbjEQKVZ (ORCPT ); Wed, 17 May 2023 06:21:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230205AbjEQKVX (ORCPT ); Wed, 17 May 2023 06:21:23 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81F2735A8 for ; Wed, 17 May 2023 03:21:20 -0700 (PDT) Received: from kwepemi500009.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4QLptd06ZhzqSKP; Wed, 17 May 2023 18:16:56 +0800 (CST) Received: from huawei.com (10.67.175.85) by kwepemi500009.china.huawei.com (7.221.188.199) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Wed, 17 May 2023 18:21:17 +0800 From: Xia Fukun To: , CC: , Subject: [PATCH v6] kobject: Fix global-out-of-bounds in kobject_action_type() Date: Wed, 17 May 2023 18:19:57 +0800 Message-ID: <20230517101957.14655-1-xiafukun@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.67.175.85] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemi500009.china.huawei.com (7.221.188.199) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following c language code can trigger KASAN's global variable out-of-bounds access error in kobject_action_type(): int main() { int fd; char *filename = "/sys/block/ram12/uevent"; char str[86] = "offline"; int len = 86; fd = open(filename, O_WRONLY); if (fd == -1) { printf("open"); exit(1); } if (write(fd, str, len) == -1) { printf("write"); exit(1); } close(fd); return 0; } Function kobject_action_type() receives the input parameters buf and count, where count is the length of the string buf. In the use case we provided, count is 86, the count_first is 85. Buf points to a string with a length of 86, and its first seven characters are "offline". In line 87 of the code, kobject_actions[action] is the string "offline" with the length of 7,an out-of-boundary access will appear: kobject_actions[action][85]. Use sysfs_match_string() to replace the fragile and convoluted loop. This function is well-tested for parsing sysfs inputs. Moreover, this modification will not cause any functional changes. Fixes: f36776fafbaa ("kobject: support passing in variables for synthetic uevents") Signed-off-by: Xia Fukun --- v5 -> v6: - Ensure that the following extensions remain effective: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-uevent v4 -> v5: - Fixed build errors and warnings, and retested the patch. v3 -> v4: - Refactor the function to be more obviously correct and readable. --- include/linux/kobject.h | 3 +++ lib/kobject_uevent.c | 30 +++++++++++++++++------------- 2 files changed, 20 insertions(+), 13 deletions(-) diff --git a/include/linux/kobject.h b/include/linux/kobject.h index c392c811d9ad..9d3ecce3c4f6 100644 --- a/include/linux/kobject.h +++ b/include/linux/kobject.h @@ -32,6 +32,9 @@ #define UEVENT_NUM_ENVP 64 /* number of env pointers */ #define UEVENT_BUFFER_SIZE 2048 /* buffer for the variables */ +/* the maximum length of the string contained in kobject_actions[] */ +#define UEVENT_KACT_STRSIZE 16 + #ifdef CONFIG_UEVENT_HELPER /* path to the userspace helper executed on an event */ extern char uevent_helper[]; diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 7c44b7ae4c5c..4030a928e9c6 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -66,7 +66,8 @@ static int kobject_action_type(const char *buf, size_t count, enum kobject_action action; size_t count_first; const char *args_start; - int ret = -EINVAL; + int i, ret = -EINVAL; + char kobj_act_buf[UEVENT_KACT_STRSIZE] = ""; if (count && (buf[count-1] == '\n' || buf[count-1] == '\0')) count--; @@ -77,21 +78,24 @@ static int kobject_action_type(const char *buf, size_t count, args_start = strnchr(buf, count, ' '); if (args_start) { count_first = args_start - buf; + if (count_first > UEVENT_KACT_STRSIZE) + goto out; + args_start = args_start + 1; + strncpy(kobj_act_buf, buf, count_first); + i = sysfs_match_string(kobject_actions, kobj_act_buf); } else - count_first = count; + i = sysfs_match_string(kobject_actions, buf); - for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) { - if (strncmp(kobject_actions[action], buf, count_first) != 0) - continue; - if (kobject_actions[action][count_first] != '\0') - continue; - if (args) - *args = args_start; - *type = action; - ret = 0; - break; - } + if (i < 0) + goto out; + + action = i; + if (args) + *args = args_start; + + *type = action; + ret = 0; out: return ret; } -- 2.17.1