Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Romain Perier <romain.perier@gmail.com>
To:     Kees Cook <keescook@chromium.org>,
        kernel-hardening@lists.openwall.com,
        Guenter Roeck <linux@roeck-us.net>
Cc:     Romain Perier <romain.perier@gmail.com>,
        linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 11/20] hwmon: Manual replacement of the deprecated strlcpy() with return values
Date:   Mon, 22 Feb 2021 16:12:22 +0100
Message-Id: <20210222151231.22572-12-romain.perier@gmail.com>
In-Reply-To: <20210222151231.22572-1-romain.perier@gmail.com>
References: <20210222151231.22572-1-romain.perier@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.
It can lead to linear read overflows, crashes, etc...

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>
---
 drivers/hwmon/pmbus/max20730.c |   66 +++++++++++++++++++++--------------------
 1 file changed, 35 insertions(+), 31 deletions(-)

diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
index 9dd3dd79bc18..a384b57b7327 100644
--- a/drivers/hwmon/pmbus/max20730.c
+++ b/drivers/hwmon/pmbus/max20730.c
@@ -107,7 +107,8 @@ struct max20730_debugfs_data {
 static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 				     size_t count, loff_t *ppos)
 {
-	int ret, len;
+	int ret;
+	ssize_t len;
 	int *idxp = file->private_data;
 	int idx = *idxp;
 	struct max20730_debugfs_data *psu = to_psu(idxp, idx);
@@ -148,13 +149,13 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 			>> MAX20730_MFR_DEVSET1_TSTAT_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "2000\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "2000\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "125\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "125\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "62.5\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "62.5\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "32\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "32\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_INTERNAL_GAIN:
 		val = (data->mfr_devset1 & MAX20730_MFR_DEVSET1_RGAIN_MASK)
@@ -163,35 +164,35 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 		if (data->id == max20734) {
 			/* AN6209 */
 			if (val == 0)
-				len = strlcpy(tbuf, "0.8\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.8\n", DEBUG_FS_DATA_MAX);
 			else if (val == 1)
-				len = strlcpy(tbuf, "3.2\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "3.2\n", DEBUG_FS_DATA_MAX);
 			else if (val == 2)
-				len = strlcpy(tbuf, "1.6\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "1.6\n", DEBUG_FS_DATA_MAX);
 			else
-				len = strlcpy(tbuf, "6.4\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "6.4\n", DEBUG_FS_DATA_MAX);
 		} else if (data->id == max20730 || data->id == max20710) {
 			/* AN6042 or AN6140 */
 			if (val == 0)
-				len = strlcpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
 			else if (val == 1)
-				len = strlcpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
 			else if (val == 2)
-				len = strlcpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
 			else
-				len = strlcpy(tbuf, "7.2\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "7.2\n", DEBUG_FS_DATA_MAX);
 		} else if (data->id == max20743) {
 			/* AN6042 */
 			if (val == 0)
-				len = strlcpy(tbuf, "0.45\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.45\n", DEBUG_FS_DATA_MAX);
 			else if (val == 1)
-				len = strlcpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
 			else if (val == 2)
-				len = strlcpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
 			else
-				len = strlcpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
 		} else {
-			len = strlcpy(tbuf, "Not supported\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "Not supported\n", DEBUG_FS_DATA_MAX);
 		}
 		break;
 	case MAX20730_DEBUGFS_BOOT_VOLTAGE:
@@ -199,26 +200,26 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 			>> MAX20730_MFR_DEVSET1_VBOOT_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "0.6484\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "0.6484\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "0.8984\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "0.8984\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "1.0\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "1.0\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_OUT_V_RAMP_RATE:
 		val = (data->mfr_devset2 & MAX20730_MFR_DEVSET2_VRATE)
 			>> MAX20730_MFR_DEVSET2_VRATE_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "4\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "4\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "2\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "2\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "1\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "1\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_OC_PROTECT_MODE:
 		ret = (data->mfr_devset2 & MAX20730_MFR_DEVSET2_OCPM_MASK)
@@ -230,13 +231,13 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 			>> MAX20730_MFR_DEVSET2_SS_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "0.75\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "0.75\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "1.5\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "1.5\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "3\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "3\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "6\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "6\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_IMAX:
 		ret = (data->mfr_devset2 & MAX20730_MFR_DEVSET2_IMAX_MASK)
@@ -287,9 +288,12 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 				"%d.%d\n", ret / 10000, ret % 10000);
 		break;
 	default:
-		len = strlcpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
+		len = strscpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
 	}
 
+	if (len == -E2BIG)
+		return -E2BIG;
+
 	return simple_read_from_buffer(buf, count, ppos, tbuf, len);
 }