[PATCH V2] regulator: core: fix constraints debug output

[Stefan Wahren <stefan.wahren@i2se.com>]

The line buffer for constraints debug isn't big enough to hold the output
in all cases. So fix the possible buffer overflow by the usage of the
scnprintf().

By the way this fixes that the debug output is overwritten
when uV_offset is greater 0.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
CC: <stable@vger.kernel.org>
---
 drivers/regulator/core.c |   43 ++++++++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 19 deletions(-)

Changes in V2:
- add fix for buffer overflow which has been noticed by Joe Perches

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index f698948..c19456e 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -780,58 +780,63 @@ static void print_constraints(struct regulator_dev *rdev)
 {
 	struct regulation_constraints *constraints = rdev->constraints;
 	char buf[80] = "";
+	size_t len = sizeof(buf) - 1;
 	int count = 0;
 	int ret;
 
 	if (constraints->min_uV && constraints->max_uV) {
 		if (constraints->min_uV == constraints->max_uV)
-			count += sprintf(buf + count, "%d mV ",
-					 constraints->min_uV / 1000);
+			count += scnprintf(buf + count, len - count, "%d mV ",
+					   constraints->min_uV / 1000);
 		else
-			count += sprintf(buf + count, "%d <--> %d mV ",
-					 constraints->min_uV / 1000,
-					 constraints->max_uV / 1000);
+			count += scnprintf(buf + count, len - count,
+					   "%d <--> %d mV ",
+					   constraints->min_uV / 1000,
+					   constraints->max_uV / 1000);
 	}
 
 	if (!constraints->min_uV ||
 	    constraints->min_uV != constraints->max_uV) {
 		ret = _regulator_get_voltage(rdev);
 		if (ret > 0)
-			count += sprintf(buf + count, "at %d mV ", ret / 1000);
+			count += scnprintf(buf + count, len - count,
+					   "at %d mV ", ret / 1000);
 	}
 
 	if (constraints->uV_offset)
-		count += sprintf(buf, "%dmV offset ",
-				 constraints->uV_offset / 1000);
+		count += scnprintf(buf + count, len - count, "%dmV offset ",
+				   constraints->uV_offset / 1000);
 
 	if (constraints->min_uA && constraints->max_uA) {
 		if (constraints->min_uA == constraints->max_uA)
-			count += sprintf(buf + count, "%d mA ",
-					 constraints->min_uA / 1000);
+			count += scnprintf(buf + count, len - count, "%d mA ",
+					   constraints->min_uA / 1000);
 		else
-			count += sprintf(buf + count, "%d <--> %d mA ",
-					 constraints->min_uA / 1000,
-					 constraints->max_uA / 1000);
+			count += scnprintf(buf + count, len - count,
+					   "%d <--> %d mA ",
+					   constraints->min_uA / 1000,
+					   constraints->max_uA / 1000);
 	}
 
 	if (!constraints->min_uA ||
 	    constraints->min_uA != constraints->max_uA) {
 		ret = _regulator_get_current_limit(rdev);
 		if (ret > 0)
-			count += sprintf(buf + count, "at %d mA ", ret / 1000);
+			count += scnprintf(buf + count, len - count,
+					   "at %d mA ", ret / 1000);
 	}
 
 	if (constraints->valid_modes_mask & REGULATOR_MODE_FAST)
-		count += sprintf(buf + count, "fast ");
+		count += scnprintf(buf + count, len - count, "fast ");
 	if (constraints->valid_modes_mask & REGULATOR_MODE_NORMAL)
-		count += sprintf(buf + count, "normal ");
+		count += scnprintf(buf + count, len - count, "normal ");
 	if (constraints->valid_modes_mask & REGULATOR_MODE_IDLE)
-		count += sprintf(buf + count, "idle ");
+		count += scnprintf(buf + count, len - count, "idle ");
 	if (constraints->valid_modes_mask & REGULATOR_MODE_STANDBY)
-		count += sprintf(buf + count, "standby");
+		count += scnprintf(buf + count, len - count, "standby");
 
 	if (!count)
-		sprintf(buf, "no parameters");
+		scnprintf(buf, len, "no parameters");
 
 	rdev_dbg(rdev, "%s\n", buf);
 
-- 
1.7.9.5