From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A111331A45; Mon, 29 Dec 2025 16:34:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767026069; cv=none; b=MjMoNA9I3HDouwztHle4Vvsuxuo5CGxZnClZ7Xn7BL5DnKPTkCBurcHU09AvXYO20h/cknNnD/OfNEXLFC+BMP7XxZ/Lw3ehwRXNxeCpK47rq+DeM4dUL6y/WE0+7pHkH3aHSdbjNWJ+Z46QVG8D4YgODTyD+YqNrVR8qFsrg9g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767026069; c=relaxed/simple; bh=7ZSmbsUe7m44dRYZw2Qr7RQ+YSUOo8zJBqgTxcY2a/E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=A/4Z5JxcAtYzCtpwooLD420zVhFpPMMIquC3+hQzg0GRKnGQ7qOOh4LjZr2RNVjfSqT9jyxBzWDXFpBmVELIce24no7RVOJKfm/DftLPLtVyx9dGZoHx/vGNKzT4mq3dTQSgNz2Cf7iaEhi5abMKZVHdgL6NxkneHAu80dBMiYs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=P+gcfS2B; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="P+gcfS2B" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25F56C4CEF7; Mon, 29 Dec 2025 16:34:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767026069; bh=7ZSmbsUe7m44dRYZw2Qr7RQ+YSUOo8zJBqgTxcY2a/E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P+gcfS2B35YdIwJctadPRsUazjgRJjPOSlZGgnnGQBbF773YFS/E0f+arUs1Mgaw8 FNaKUhsQ+vI//p8fdDmRnpYayC3O1UeCAe3+GaMzFv/C5wesbT9/Ms7yj9WAA5m4Jh 8YY90gPntYMy2XzU6x9lJAyM8piUi/9ZU/r9Isbo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gui-Dong Han , Guenter Roeck Subject: [PATCH 6.18 421/430] hwmon: (w83791d) Convert macros to functions to avoid TOCTOU Date: Mon, 29 Dec 2025 17:13:43 +0100 Message-ID: <20251229160739.805458858@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251229160724.139406961@linuxfoundation.org> References: <20251229160724.139406961@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gui-Dong Han commit 670d7ef945d3a84683594429aea6ab2cdfa5ceb4 upstream. The macro FAN_FROM_REG evaluates its arguments multiple times. When used in lockless contexts involving shared driver data, this leads to Time-of-Check to Time-of-Use (TOCTOU) race conditions, potentially causing divide-by-zero errors. Convert the macro to a static function. This guarantees that arguments are evaluated only once (pass-by-value), preventing the race conditions. Additionally, in store_fan_div, move the calculation of the minimum limit inside the update lock. This ensures that the read-modify-write sequence operates on consistent data. Adhere to the principle of minimal changes by only converting macros that evaluate arguments multiple times and are used in lockless contexts. Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/ Fixes: 9873964d6eb2 ("[PATCH] HWMON: w83791d: New hardware monitoring driver for the Winbond W83791D") Cc: stable@vger.kernel.org Signed-off-by: Gui-Dong Han Link: https://lore.kernel.org/r/20251202180105.12842-1-hanguidong02@gmail.com Signed-off-by: Guenter Roeck Signed-off-by: Greg Kroah-Hartman --- drivers/hwmon/w83791d.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) --- a/drivers/hwmon/w83791d.c +++ b/drivers/hwmon/w83791d.c @@ -218,9 +218,14 @@ static u8 fan_to_reg(long rpm, int div) return clamp_val((1350000 + rpm * div / 2) / (rpm * div), 1, 254); } -#define FAN_FROM_REG(val, div) ((val) == 0 ? -1 : \ - ((val) == 255 ? 0 : \ - 1350000 / ((val) * (div)))) +static int fan_from_reg(int val, int div) +{ + if (val == 0) + return -1; + if (val == 255) + return 0; + return 1350000 / (val * div); +} /* for temp1 which is 8-bit resolution, LSB = 1 degree Celsius */ #define TEMP1_FROM_REG(val) ((val) * 1000) @@ -521,7 +526,7 @@ static ssize_t show_##reg(struct device struct w83791d_data *data = w83791d_update_device(dev); \ int nr = sensor_attr->index; \ return sprintf(buf, "%d\n", \ - FAN_FROM_REG(data->reg[nr], DIV_FROM_REG(data->fan_div[nr]))); \ + fan_from_reg(data->reg[nr], DIV_FROM_REG(data->fan_div[nr]))); \ } show_fan_reg(fan); @@ -585,10 +590,10 @@ static ssize_t store_fan_div(struct devi if (err) return err; + mutex_lock(&data->update_lock); /* Save fan_min */ - min = FAN_FROM_REG(data->fan_min[nr], DIV_FROM_REG(data->fan_div[nr])); + min = fan_from_reg(data->fan_min[nr], DIV_FROM_REG(data->fan_div[nr])); - mutex_lock(&data->update_lock); data->fan_div[nr] = div_to_reg(nr, val); switch (nr) {