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 555F6C77B7A for ; Tue, 16 May 2023 12:38:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233161AbjEPMir (ORCPT ); Tue, 16 May 2023 08:38:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231721AbjEPMip (ORCPT ); Tue, 16 May 2023 08:38:45 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C66CE170E for ; Tue, 16 May 2023 05:38:43 -0700 (PDT) Received: from kwepemi500009.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4QLFzf4xH9z18LRM; Tue, 16 May 2023 20:34:22 +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; Tue, 16 May 2023 20:38:41 +0800 From: Xia Fukun To: , CC: , Subject: [PATCH v5] kobject: Fix global-out-of-bounds in kobject_action_type() Date: Tue, 16 May 2023 20:37:19 +0800 Message-ID: <20230516123719.117137-1-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: dggems704-chm.china.huawei.com (10.3.19.181) 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 --- v4 -> v5: - Fixed build errors and warnings, and retested the patch. v3 -> v4: - Refactor the function to be more obviously correct and readable. --- lib/kobject_uevent.c | 32 +++++++++++++++----------------- 1 file changed, 15 insertions(+), 17 deletions(-) diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 7c44b7ae4c5c..1ec20a7d3d45 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -64,9 +64,8 @@ static int kobject_action_type(const char *buf, size_t count, const char **args) { enum kobject_action action; - size_t count_first; const char *args_start; - int ret = -EINVAL; + int i, ret = -EINVAL; if (count && (buf[count-1] == '\n' || buf[count-1] == '\0')) count--; @@ -75,23 +74,22 @@ static int kobject_action_type(const char *buf, size_t count, goto out; args_start = strnchr(buf, count, ' '); - if (args_start) { - count_first = args_start - buf; + if (args_start) args_start = args_start + 1; - } else - count_first = count; - 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; - } + /* Use sysfs_match_string() to replace the fragile and convoluted loop */ + i = sysfs_match_string(kobject_actions, buf); + + if (i < 0) + return ret; + + action = i; + + if (args) + *args = args_start; + + *type = action; + ret = 0; out: return ret; } -- 2.17.1