From patchwork Tue Sep 24 17:47:28 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Nick Desaulniers X-Patchwork-Id: 11159299 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 3501114ED for ; Tue, 24 Sep 2019 17:47:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 070012146E for ; Tue, 24 Sep 2019 17:47:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="seXQRnG4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407577AbfIXRrd (ORCPT ); Tue, 24 Sep 2019 13:47:33 -0400 Received: from mail-qt1-f202.google.com ([209.85.160.202]:56885 "EHLO mail-qt1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404360AbfIXRrd (ORCPT ); Tue, 24 Sep 2019 13:47:33 -0400 Received: by mail-qt1-f202.google.com with SMTP id m6so2796112qtk.23 for ; Tue, 24 Sep 2019 10:47:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc:content-transfer-encoding; bh=DBG/wFyung5W8UWO8gFujad4LCgDfce9k3vKq6AZOHc=; b=seXQRnG46I6Ci9HSw67oM4f9WU5RkjmQX2F1eTZvaF10NZJKm/ILV0ZrtVikdF+Sl/ sgcA8DGRARP+NC27ixqtahqQ0TrX25UIlrcGpQs+2UU0fZx/OfPejIjIWx60N/VQw8pA e6XQMVBYmrhl/IdQnJ/tnYp0/5QdvCbanCSHTfeiKlV8eqmTujwDoJyjjFzHm1blLi+t msRPBmg70+21BGQqQWSLUWVo2HCcjgEJGsFkj9eqJZAFg95KvDAUA/DbgOzTiEpwFmr8 q378DkEh/bKx4RYUt6EgDvf68S88RRjlndPnuornArPd7L1ZTGixqCCQwb94iO4mGkve hfeA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc:content-transfer-encoding; bh=DBG/wFyung5W8UWO8gFujad4LCgDfce9k3vKq6AZOHc=; b=r6+PEDayatADqir2tZKK2HS8E9jHYiNLeNLBXgMXrHrnEdn5NDTzKwpV8Ios8doK/i ic778HKEvtOGtyQ3jn98j/8oGxdQQtb5YaTAzpKevoeACZun947SEDU6SlQ8NIUdDm2S IntmDw8E1dPZXUzPPzK1BNTPiJpQdGDjCCxCK83Zr7KNl+XDrlMtx+BAjfa80CNXm1I3 uIXBwA1jnZYgdSf4CD428e9aIcy/hSltuJF8gWdz8PeF7mhDjICe9SspwP9JzhxFO9Uj R6nlk1C3Goey5XUm9VuP+DDyZpSBFIfAqbw3olr2XTeQu7m8dRJFFEjdellEQ+t7hbbn EIig== X-Gm-Message-State: APjAAAVRBFlLuojyAfDIi8WKTm5y6TLYxF3l2TlXvVhRVpDTSqHLAK5Q POGED+H7d7fmMdm+s2jFx3SsfyU2i8qi4yNKrDY= X-Google-Smtp-Source: APXvYqxqiZGW0UgAYDRxKRJCktP8tpY/Jew2d6NDW6FIJf4VUr2P6v9BiY4203WhfvWsdVfDNVdf5kMzk37Yk2qyDcc= X-Received: by 2002:ae9:f404:: with SMTP id y4mr3717758qkl.225.1569347252597; Tue, 24 Sep 2019 10:47:32 -0700 (PDT) Date: Tue, 24 Sep 2019 10:47:28 -0700 In-Reply-To: Message-Id: <20190924174728.201464-1-ndesaulniers@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.23.0.351.gc4317032e6-goog Subject: [PATCH v2] hwmon: (applesmc) fix UB and udelay overflow From: Nick Desaulniers To: linux@roeck-us.net Cc: clang-built-linux@googlegroups.com, jdelvare@suse.com, Nick Desaulniers , " =?utf-8?q?Tomasz_Pawe=C5=82_G?= =?utf-8?q?ajc?= " , Nathan Chancellor , Henrik Rydberg , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org Sender: linux-hwmon-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org Fixes the following 2 issues in the driver: 1. Left shifting a signed integer is undefined behavior. Unsigned integral types should be used for bitwise operations. 2. The delay scales from 0x0010 to 0x20000 by powers of 2, but udelay will result in a linkage failure when given a constant that's greater than 20000 (0x4E20). Agressive loop unrolling can fully unroll the loop, resulting in later iterations overflowing the call to udelay. 2 is fixed via splitting the loop in two, iterating the first up to the point where udelay would overflow, then switching to mdelay, as suggested in Documentation/timers/timers-howto.rst. Reported-by: Tomasz Paweł Gajc Link: https://github.com/ClangBuiltLinux/linux/issues/678 Debugged-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Reviewed-by: Cengiz Can --- Changes V1 -> V2: * The first loop in send_byte() needs to break out on the same condition now. Technically, the loop condition could even be removed. The diff looks funny because of the duplicated logic between existing and newly added for loops. drivers/hwmon/applesmc.c | 35 +++++++++++++++++++++++++++++++---- 1 file changed, 31 insertions(+), 4 deletions(-) diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c index 183ff3d25129..c76adb504dff 100644 --- a/drivers/hwmon/applesmc.c +++ b/drivers/hwmon/applesmc.c @@ -46,6 +46,7 @@ #define APPLESMC_MIN_WAIT 0x0010 #define APPLESMC_RETRY_WAIT 0x0100 #define APPLESMC_MAX_WAIT 0x20000 +#define APPLESMC_UDELAY_MAX 20000 #define APPLESMC_READ_CMD 0x10 #define APPLESMC_WRITE_CMD 0x11 @@ -157,14 +158,23 @@ static struct workqueue_struct *applesmc_led_wq; static int wait_read(void) { u8 status; - int us; - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { + unsigned int us; + + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_UDELAY_MAX; us <<= 1) { udelay(us); status = inb(APPLESMC_CMD_PORT); /* read: wait for smc to settle */ if (status & 0x01) return 0; } + /* switch to mdelay for longer sleeps */ + for (; us < APPLESMC_MAX_WAIT; us <<= 1) { + mdelay(us); + status = inb(APPLESMC_CMD_PORT); + /* read: wait for smc to settle */ + if (status & 0x01) + return 0; + } pr_warn("wait_read() fail: 0x%02x\n", status); return -EIO; @@ -177,10 +187,10 @@ static int wait_read(void) static int send_byte(u8 cmd, u16 port) { u8 status; - int us; + unsigned int us; outb(cmd, port); - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_UDELAY_MAX; us <<= 1) { udelay(us); status = inb(APPLESMC_CMD_PORT); /* write: wait for smc to settle */ @@ -190,6 +200,23 @@ static int send_byte(u8 cmd, u16 port) if (status & 0x04) return 0; /* timeout: give up */ + if (us << 1 == APPLESMC_UDELAY_MAX) + break; + /* busy: long wait and resend */ + udelay(APPLESMC_RETRY_WAIT); + outb(cmd, port); + } + /* switch to mdelay for longer sleeps */ + for (; us < APPLESMC_MAX_WAIT; us <<= 1) { + mdelay(us); + status = inb(APPLESMC_CMD_PORT); + /* write: wait for smc to settle */ + if (status & 0x02) + continue; + /* ready: cmd accepted, return */ + if (status & 0x04) + return 0; + /* timeout: give up */ if (us << 1 == APPLESMC_MAX_WAIT) break; /* busy: long wait and resend */