From patchwork Mon Nov 13 19:38:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 13454387 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 94DA123753; Mon, 13 Nov 2023 19:38:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GLS9dTAx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16CCBC433C7; Mon, 13 Nov 2023 19:38:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699904296; bh=9ypxMPYW+WDYaCwDSx2ywc4K+xykb9J09UJjGSMapQ0=; h=Date:From:To:Cc:Subject:From; b=GLS9dTAxfC37erUQoZRNm07gmEetbMSbdz21/QTHmqATocVHj+fiVqy2wC74hZNmw 7IFD8yZQ2cjRhShv6szxx/Dsami6m4C9f9Y+/TaGCEDXL6VCcL8DjEXAmcKtARaPjN mPC9+hLH+MPrqEJuEN4c21The29qeOsqCLDHaPXiEWEiZ+D4MQ8eykPD7XagFSK8W7 255n+Dj8RfSUDZIs3BnheuHtBqGWvb4GTZLJ0TQQZiqdh944QE0w7XadC7qM5rIfRY XjdaZObL4CPLZLjtP1aaPCy0ei1f/Zu0w7mwrGPTuDaU97ZFmj7xIwNDzb7DBgqEAU 8tmHHmYelCDxg== Date: Mon, 13 Nov 2023 13:38:12 -0600 From: "Gustavo A. R. Silva" To: Jean Delvare , Guenter Roeck , Joel Stanley , Andrew Jeffery Cc: linux-hwmon@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" , linux-hardening@vger.kernel.org Subject: [PATCH][next] hwmon: (aspeed-pwm-tacho) Fix -Wstringop-overflow warning in aspeed_create_fan_tach_channel() Message-ID: Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Based on the documentation below, the maximum number of Fan tach channels is 16: Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt:45: 45 - aspeed,fan-tach-ch : should specify the Fan tach input channel. 46 integer value in the range 0 through 15, with 0 indicating 47 Fan tach channel 0 and 15 indicating Fan tach channel 15. 48 At least one Fan tach input channel is required. However, the compiler doesn't know that, and legitimaly warns about a potential overwrite in array `u8 fan_tach_ch_source[16]` in `struct aspeed_pwm_tacho_data`, in case `index` takes a value outside the boundaries of the array: drivers/hwmon/aspeed-pwm-tacho.c: 179 struct aspeed_pwm_tacho_data { ... 184 bool fan_tach_present[16]; ... 193 u8 fan_tach_ch_source[16]; ... 196 }; In function ‘aspeed_create_fan_tach_channel’, inlined from ‘aspeed_create_fan’ at drivers/hwmon/aspeed-pwm-tacho.c:877:2, inlined from ‘aspeed_pwm_tacho_probe’ at drivers/hwmon/aspeed-pwm-tacho.c:936:9: drivers/hwmon/aspeed-pwm-tacho.c:751:49: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=] 751 | priv->fan_tach_ch_source[index] = pwm_source; | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~ drivers/hwmon/aspeed-pwm-tacho.c: In function ‘aspeed_pwm_tacho_probe’: drivers/hwmon/aspeed-pwm-tacho.c:193:12: note: at offset [48, 255] into destination object ‘fan_tach_ch_source’ of size 16 193 | u8 fan_tach_ch_source[16]; | ^~~~~~~~~~~~~~~~~~ Fix this by sanity checking `index` before using it to index arrays of size 16 elements in `struct aspeed_pwm_tacho_data`. Also, and just for completeness, add a `pr_err()` message to display in the unlikely case `0 > index >= 16`. This is probably the last remaining -Wstringop-overflow issue in the kernel, and this patch helps with the ongoing efforts to enable such compiler option globally. Signed-off-by: Gustavo A. R. Silva --- drivers/hwmon/aspeed-pwm-tacho.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c index 997df4b40509..092a81916325 100644 --- a/drivers/hwmon/aspeed-pwm-tacho.c +++ b/drivers/hwmon/aspeed-pwm-tacho.c @@ -166,6 +166,8 @@ #define MAX_CDEV_NAME_LEN 16 +#define MAX_ASPEED_FAN_TACH_CHANNELS 16 + struct aspeed_cooling_device { char name[16]; struct aspeed_pwm_tacho_data *priv; @@ -181,7 +183,7 @@ struct aspeed_pwm_tacho_data { struct reset_control *rst; unsigned long clk_freq; bool pwm_present[8]; - bool fan_tach_present[16]; + bool fan_tach_present[MAX_ASPEED_FAN_TACH_CHANNELS]; u8 type_pwm_clock_unit[3]; u8 type_pwm_clock_division_h[3]; u8 type_pwm_clock_division_l[3]; @@ -190,7 +192,7 @@ struct aspeed_pwm_tacho_data { u16 type_fan_tach_unit[3]; u8 pwm_port_type[8]; u8 pwm_port_fan_ctrl[8]; - u8 fan_tach_ch_source[16]; + u8 fan_tach_ch_source[MAX_ASPEED_FAN_TACH_CHANNELS]; struct aspeed_cooling_device *cdev[8]; const struct attribute_group *groups[3]; }; @@ -746,10 +748,14 @@ static void aspeed_create_fan_tach_channel(struct aspeed_pwm_tacho_data *priv, for (val = 0; val < count; val++) { index = fan_tach_ch[val]; - aspeed_set_fan_tach_ch_enable(priv->regmap, index, true); - priv->fan_tach_present[index] = true; - priv->fan_tach_ch_source[index] = pwm_source; - aspeed_set_fan_tach_ch_source(priv->regmap, index, pwm_source); + if (index < MAX_ASPEED_FAN_TACH_CHANNELS) { + aspeed_set_fan_tach_ch_enable(priv->regmap, index, true); + priv->fan_tach_present[index] = true; + priv->fan_tach_ch_source[index] = pwm_source; + aspeed_set_fan_tach_ch_source(priv->regmap, index, pwm_source); + } else { + pr_err("Invalid Fan Tach input channel %u\n.", index); + } } }