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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, 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 D4630C43387 for ; Sat, 12 Jan 2019 15:29:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD5A62086C for ; Sat, 12 Jan 2019 15:29:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726514AbfALP3S (ORCPT ); Sat, 12 Jan 2019 10:29:18 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:34296 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726436AbfALP3J (ORCPT ); Sat, 12 Jan 2019 10:29:09 -0500 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id x0CFSs2Q026603; Sat, 12 Jan 2019 16:28:54 +0100 From: Willy Tarreau To: Silvio Cesare Cc: linux-kernel@vger.kernel.org, Mark Brown , Dan Carpenter , Kees Cook , Will Deacon , Greg KH Subject: [PATCH 8/8] spi: dw: change snprintf to scnprintf for possible overflow Date: Sat, 12 Jan 2019 16:28:44 +0100 Message-Id: <20190112152844.26550-8-w@1wt.eu> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20190112152844.26550-1-w@1wt.eu> References: <20190112152844.26550-1-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Silvio Cesare Change snprintf to scnprintf. There are generally two cases where using snprintf causes problems. 1) Uses of size += snprintf(buf, SIZE - size, fmt, ...) In this case, if snprintf would have written more characters than what the buffer size (SIZE) is, then size will end up larger than SIZE. In later uses of snprintf, SIZE - size will result in a negative number, leading to problems. Note that size might already be too large by using size = snprintf before the code reaches a case of size += snprintf. 2) If size is ultimately used as a length parameter for a copy back to user space, then it will potentially allow for a buffer overflow and information disclosure when size is greater than SIZE. When the size is used to index the buffer directly, we can have memory corruption. This also means when size = snprintf... is used, it may also cause problems since size may become large. Copying to userspace is mitigated by the HARDENED_USERCOPY kernel configuration. The solution to these issues is to use scnprintf which returns the number of characters actually written to the buffer, so the size variable will never exceed SIZE. Signed-off-by: Silvio Cesare Cc: Mark Brown Cc: Dan Carpenter Cc: Kees Cook Cc: Will Deacon Cc: Greg KH Signed-off-by: Willy Tarreau --- drivers/spi/spi-dw.c | 36 ++++++++++++++++++------------------ 1 file changed, 18 insertions(+), 18 deletions(-) diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c index b705f2bdb8b9..008d52d37439 100644 --- a/drivers/spi/spi-dw.c +++ b/drivers/spi/spi-dw.c @@ -54,41 +54,41 @@ static ssize_t dw_spi_show_regs(struct file *file, char __user *user_buf, if (!buf) return 0; - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "%s registers:\n", dev_name(&dws->master->dev)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "=================================\n"); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "CTRL0: \t\t0x%08x\n", dw_readl(dws, DW_SPI_CTRL0)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "CTRL1: \t\t0x%08x\n", dw_readl(dws, DW_SPI_CTRL1)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "SSIENR: \t0x%08x\n", dw_readl(dws, DW_SPI_SSIENR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "SER: \t\t0x%08x\n", dw_readl(dws, DW_SPI_SER)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "BAUDR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_BAUDR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "TXFTLR: \t0x%08x\n", dw_readl(dws, DW_SPI_TXFLTR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "RXFTLR: \t0x%08x\n", dw_readl(dws, DW_SPI_RXFLTR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "TXFLR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_TXFLR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "RXFLR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_RXFLR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "SR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_SR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "IMR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_IMR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "ISR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_ISR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "DMACR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_DMACR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "DMATDLR: \t0x%08x\n", dw_readl(dws, DW_SPI_DMATDLR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "DMARDLR: \t0x%08x\n", dw_readl(dws, DW_SPI_DMARDLR)); - len += snprintf(buf + len, SPI_REGS_BUFSIZE - len, + len += scnprintf(buf + len, SPI_REGS_BUFSIZE - len, "=================================\n"); ret = simple_read_from_buffer(user_buf, count, ppos, buf, len); -- 2.19.2