[PATCH v2] drivers/iio: Remove all strcpy() uses in favor of strscpy()

[Len Baker <len.baker@gmx.com>]

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. The safe replacement is strscpy().

This patch is an effort to clean up the proliferation of str*()
functions in the kernel and a previous step in the path to remove
the strcpy function from the kernel entirely [1].

[1] https://github.com/KSPP/linux/issues/88

Signed-off-by: Len Baker <len.baker@gmx.com>
---
Changelog v1 -> v2
- Modify the commit changelog to inform that the motivation of this
  patch is to remove the strcpy() function from the kernel entirely
  (Jonathan Cameron).

 drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c
index f282e9cc34c5..3a6aa1c4bf6c 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_magn.c
@@ -264,6 +264,7 @@ int inv_mpu_magn_set_orient(struct inv_mpu6050_state *st)
 	const char *orient;
 	char *str;
 	int i;
+	size_t n;

 	/* fill magnetometer orientation */
 	switch (st->chip_type) {
@@ -282,17 +283,18 @@ int inv_mpu_magn_set_orient(struct inv_mpu6050_state *st)
 		for (i = 0; i < 3; ++i) {
 			orient = st->orientation.rotation[6 + i];
 			/* use length + 2 for adding minus sign if needed */
-			str = devm_kzalloc(regmap_get_device(st->map),
-					   strlen(orient) + 2, GFP_KERNEL);
+			n = strlen(orient) + 2;
+			str = devm_kzalloc(regmap_get_device(st->map), n,
+					   GFP_KERNEL);
 			if (str == NULL)
 				return -ENOMEM;
 			if (strcmp(orient, "0") == 0) {
-				strcpy(str, orient);
+				strscpy(str, orient, n);
 			} else if (orient[0] == '-') {
-				strcpy(str, &orient[1]);
+				strscpy(str, &orient[1], n);
 			} else {
 				str[0] = '-';
-				strcpy(&str[1], orient);
+				strscpy(&str[1], orient, n - 1);
 			}
 			st->magn_orient.rotation[6 + i] = str;
 		}
--
2.25.1