patch "iio: addac: ad74413r: fix integer promotion bug in" added to char-misc-testing

This is a note to let you know that I've just added the patch titled

iio: addac: ad74413r: fix integer promotion bug in

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From 980389d06d08442fad0139874bff455c76125e47 Mon Sep 17 00:00:00 2001
From: Rasmus Villemoes <[email protected]>
Date: Fri, 18 Nov 2022 13:32:08 +0100
Subject: iio: addac: ad74413r: fix integer promotion bug in
ad74413_get_input_current_offset()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The constant AD74413R_ADC_RESULT_MAX is defined via GENMASK, so its type is "unsigned long".

Hence in the expression voltage_offset * AD74413R_ADC_RESULT_MAX, voltage_offset is first promoted to unsigned long, and since it may be negative, that results in a garbage value. For example, when range is AD74413R_ADC_RANGE_5V_BI_DIR, voltage_offset is -2500 and voltage_range is 5000, so the RHS of this assignment is, depending on sizeof(long), either 826225UL or 3689348814709142UL, which after truncation to int then results in either 826225 or 1972216214 being the output from in_currentX_offset.

Casting to int avoids that promotion and results in the correct -32767 output.

---
 drivers/iio/addac/ad74413r.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 899bcd83f40b..e0e130ba9d3e 100644
@@ -691,7 +691,7 @@ static int ad74413_get_input_current_offset(struct ad74413r_state *st,
 	if (ret)
 		return ret;
 
-	*val = voltage_offset * AD74413R_ADC_RESULT_MAX / voltage_range;
+	*val = voltage_offset * (int)AD74413R_ADC_RESULT_MAX / voltage_range;
 
 	return IIO_VAL_INT;
 }

2.38.1