linux-hardening - [PATCH v2] iio: sx9324: avoid copying property strings

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Date: Thu, 26 Oct 2023 23:53:28 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v2] iio: sx9324: avoid copying property strings

We're doing some needless string copies when trying to assign the proper
`prop` string. We can make `prop` a const char* and simply assign to
string literals.

For the case where a format string is used, let's allocate some memory
via kasprintf() and point prop to it.

This also cleans up some deprecated strncpy() uses [1].

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Changes in v2:
- make prop a const char* and do simple assignments (thanks Jonathan)
- rebase onto 3a568e3a961ba330
- Link to v1: https://lore.kernel.org/r/20230921-strncpy-drivers-iio-proximity-sx9324-c-v1-1-4e8d28fd1e7c@google.com
---
Note: build-tested
---
 drivers/iio/proximity/sx9324.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/proximity/sx9324.c b/drivers/iio/proximity/sx9324.c
index 438f9c9aba6e..c8547035cb47 100644
--- a/drivers/iio/proximity/sx9324.c
+++ b/drivers/iio/proximity/sx9324.c
@@ -885,7 +885,7 @@ sx9324_get_default_reg(struct device *dev, int idx,
 #define SX9324_RESOLUTION_DEF "semtech,ph01-resolution"
 #define SX9324_PROXRAW_DEF "semtech,ph01-proxraw-strength"
 	unsigned int pin_defs[SX9324_NUM_PINS];
-	char prop[] = SX9324_PROXRAW_DEF;
+	const char *prop = SX9324_PROXRAW_DEF;
 	u32 start = 0, raw = 0, pos = 0;
 	int ret, count, ph, pin;
 	const char *res;
@@ -899,7 +899,7 @@ sx9324_get_default_reg(struct device *dev, int idx,
 	case SX9324_REG_AFE_PH2:
 	case SX9324_REG_AFE_PH3:
 		ph = reg_def->reg - SX9324_REG_AFE_PH0;
-		snprintf(prop, ARRAY_SIZE(prop), "semtech,ph%d-pin", ph);
+		prop = kasprintf(GFP_KERNEL, "semtech,ph%d-pin", ph);
 
 		count = device_property_count_u32(dev, prop);
 		if (count != ARRAY_SIZE(pin_defs))
@@ -913,6 +913,7 @@ sx9324_get_default_reg(struct device *dev, int idx,
 			raw |= (pin_defs[pin] << (2 * pin)) &
 			       SX9324_REG_AFE_PH0_PIN_MASK(pin);
 		reg_def->def = raw;
+		kfree(prop);
 		break;
 	case SX9324_REG_AFE_CTRL0:
 		ret = device_property_read_string(dev,
@@ -937,11 +938,9 @@ sx9324_get_default_reg(struct device *dev, int idx,
 	case SX9324_REG_AFE_CTRL4:
 	case SX9324_REG_AFE_CTRL7:
 		if (reg_def->reg == SX9324_REG_AFE_CTRL4)
-			strncpy(prop, "semtech,ph01-resolution",
-				ARRAY_SIZE(prop));
+			prop = "semtech,ph01-resolution";
 		else
-			strncpy(prop, "semtech,ph23-resolution",
-				ARRAY_SIZE(prop));
+			prop = "semtech,ph23-resolution";
 
 		ret = device_property_read_u32(dev, prop, &raw);
 		if (ret)
@@ -1012,11 +1011,9 @@ sx9324_get_default_reg(struct device *dev, int idx,
 	case SX9324_REG_PROX_CTRL0:
 	case SX9324_REG_PROX_CTRL1:
 		if (reg_def->reg == SX9324_REG_PROX_CTRL0)
-			strncpy(prop, "semtech,ph01-proxraw-strength",
-				ARRAY_SIZE(prop));
+			prop = "semtech,ph01-proxraw-strength";
 		else
-			strncpy(prop, "semtech,ph23-proxraw-strength",
-				ARRAY_SIZE(prop));
+			prop = "semtech,ph23-proxraw-strength";
 		ret = device_property_read_u32(dev, prop, &raw);
 		if (ret)
 			break;

---
base-commit: 3a568e3a961ba330091cd031647e4c303fa0badb
change-id: 20230921-strncpy-drivers-iio-proximity-sx9324-c-8c3437676039

Best regards,
--
Justin Stitt <justinstitt@...gle.com>