From patchwork Thu Jun 3 17:12:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= X-Patchwork-Id: 453378 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53F04C47096 for ; Thu, 3 Jun 2021 17:14:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33CD461402 for ; Thu, 3 Jun 2021 17:14:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233267AbhFCRP7 (ORCPT ); Thu, 3 Jun 2021 13:15:59 -0400 Received: from mail-wr1-f41.google.com ([209.85.221.41]:45679 "EHLO mail-wr1-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233268AbhFCROE (ORCPT ); Thu, 3 Jun 2021 13:14:04 -0400 Received: by mail-wr1-f41.google.com with SMTP id z8so6578618wrp.12 for ; Thu, 03 Jun 2021 10:12:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=eTjd03y8TglinzqMGJIZSRr/9URvtjInPh0BcY13G+A=; b=WAxZiPnsjuq//CH74fMuCOVEQhD05UkkjHeFJX9hz56/StO3WRQGBK4xJ/3ZnXbq3C R3G2st+gNPrnpdDLMvyHlJLlPO4YaLGQZ9GTCg9W6QscPAlrnHibI+5YFugkxkhFqhBF 8btBBpQucPeTSMGVWyOIDQN/leA7UJh3J0UMKqA6jCq96PYbMrcqdvm097cpx0W3U3pF a1ClxbMcL00gYlUgab6BP37XuIg7XfOJoraZw/8fQTeIyL0QDvpMPsLKP0S7u8N0JXn3 paR9FaIP/QS4Y7ppjP4ioifWnSX+3pPf03bNRXZWjz/+J9/pZ3+FycqObBLOYSyumYZz qmBg== X-Gm-Message-State: AOAM531+kjlykqqkqu5MauJOqd1tYpf4LxI3FIy4oyGY4EllOxT5YX4b IZOKp25J2udzA9Iu6p9xqWQ= X-Google-Smtp-Source: ABdhPJy+aEMYLnucqADPTV4X7gNRDJeJA/lbF7xl/47a7W08zsp7Nuo1xFWSO1YbuVngOGn4WqkKKQ== X-Received: by 2002:a05:6000:233:: with SMTP id l19mr65690wrz.34.1622740323389; Thu, 03 Jun 2021 10:12:03 -0700 (PDT) Received: from workstation.lan ([95.155.85.46]) by smtp.gmail.com with ESMTPSA id r5sm1790945wmh.18.2021.06.03.10.12.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Jun 2021 10:12:02 -0700 (PDT) From: =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= To: "Rafael J. Wysocki" Cc: Bjorn Helgaas , Len Brown , Lance Ortiz , Joe Perches , linux-acpi@vger.kernel.org Subject: [PATCH] ACPI: sysfs: Fix a buffer overrun problem with description_show() Date: Thu, 3 Jun 2021 17:12:01 +0000 Message-Id: <20210603171201.801071-1-kw@linux.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Currently, a device description can be obtained using ACPI, if the _STR method exists for a particular device, and then exposed to the userspace via a sysfs object as a string value. If the _STR method is available for a given device then the data (usually a Unicode string) is read and stored in a buffer (of the ACPI_TYPE_BUFFER type) with a pointer to said buffer cached in the struct acpi_device_pnp for later access. The description_show() function is responsible for exposing the device description to the userspace via a corresponding sysfs object and internally calls the utf16s_to_utf8s() function with a pointer to the buffer that contains the Unicode string so that it can be converted from UTF16 encoding to UTF8 and thus allowing for the value to be safely stored and later displayed. When invoking the utf16s_to_utf8s() function, the description_show() function also sets a limit of the data that can be saved into a provided buffer as a result of the character conversion to be a total of PAGE_SIZE, and upon completion, the utf16s_to_utf8s() function returns an integer value denoting the number of bytes that have been written into the provided buffer. Following the execution of the utf16s_to_utf8s() a newline character will be added at the end of the resulting buffer so that when the value is read in the userspace through the sysfs object then it would include newline making it more accessible when working with the sysfs file system in the shell, etc. Normally, this wouldn't be a problem, but if the function utf16s_to_utf8s() happens to return the number of bytes written to be precisely PAGE_SIZE, then we would overrun the buffer and write the newline character outside the allotted space which can have undefined consequences or result in a failure. To fix this buffer overrun, ensure that there always is enough space left for the newline character to be safely appended. Fixes: d1efe3c324ea ("ACPI: Add new sysfs interface to export device description") Signed-off-by: Krzysztof Wilczyński Reviewed-by: Bjorn Helgaas --- drivers/acpi/device_sysfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c index fa2c1c93072c..a393e0e09381 100644 --- a/drivers/acpi/device_sysfs.c +++ b/drivers/acpi/device_sysfs.c @@ -448,7 +448,7 @@ static ssize_t description_show(struct device *dev, (wchar_t *)acpi_dev->pnp.str_obj->buffer.pointer, acpi_dev->pnp.str_obj->buffer.length, UTF16_LITTLE_ENDIAN, buf, - PAGE_SIZE); + PAGE_SIZE - 1); buf[result++] = '\n';