[RFC 2/7] Input: joystick - avoid fragile snprintf use

[Rasmus Villemoes]

Passing overlapping src and dst buffers to snprintf is fragile, and
while it currently works for the special case of passing dst as the
argument corresponding to an initial "%s" in the format string, any
other use would very likely lead to chaos. It's easy enough to avoid,
so let's do that.

Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
 drivers/input/joystick/analog.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index 6f8b084e13d0..d0a9b90e8f94 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -435,14 +435,16 @@ static void analog_calibrate_timer(struct analog_port *port)
 
 static void analog_name(struct analog *analog)
 {
-	snprintf(analog->name, sizeof(analog->name), "Analog %d-axis %d-button",
+	int ret = 0;
+
+	ret = scnprintf(analog->name, sizeof(analog->name), "Analog %d-axis %d-button",
 		 hweight8(analog->mask & ANALOG_AXES_STD),
 		 hweight8(analog->mask & ANALOG_BTNS_STD) + !!(analog->mask & ANALOG_BTNS_CHF) * 2 +
 		 hweight16(analog->mask & ANALOG_BTNS_GAMEPAD) + !!(analog->mask & ANALOG_HBTN_CHF) * 4);
 
 	if (analog->mask & ANALOG_HATS_ALL)
-		snprintf(analog->name, sizeof(analog->name), "%s %d-hat",
-			 analog->name, hweight16(analog->mask & ANALOG_HATS_ALL));
+		scnprintf(analog->name + ret, sizeof(analog->name) - ret, " %d-hat",
+			  hweight16(analog->mask & ANALOG_HATS_ALL));
 
 	if (analog->mask & ANALOG_HAT_FCS)
 		strlcat(analog->name, " FCS", sizeof(analog->name));
-- 
2.1.4