[PATCH] [v2] Input: analog - fix invalid snprintf() call

[Arnd Bergmann]

From: Arnd Bergmann <a...@arndb.de>

Overlapping input and output arguments to snprintf() are
undefined behavior in C99:

drivers/input/joystick/analog.c: In function 'analog_name':
drivers/input/joystick/analog.c:428:3: error: 'snprintf' argument 4 overlaps 
destination object 'analog' [-Werror=restrict]
  428 |   snprintf(analog->name, sizeof(analog->name), "%s %d-hat",
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  429 |     analog->name, hweight16(analog->mask & ANALOG_HATS_ALL));
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/input/joystick/analog.c:420:40: note: destination object referenced by 
'restrict'-qualified argument 1 was declared here
  420 | static void analog_name(struct analog *analog)
      |                         ~~~~~~~~~~~~~~~^~~~~~

Change this function to use the simpler seq_buf interface instead.

Cc: Rasmus Villemoes <rasmus.villem...@prevas.dk>
Signed-off-by: Arnd Bergmann <a...@arndb.de>
---
v2: use seq_buf instead of rolling my own
---
 drivers/input/joystick/analog.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index f798922a4598..087b65ae7585 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -19,6 +19,7 @@
 #include <linux/input.h>
 #include <linux/gameport.h>
 #include <linux/jiffies.h>
+#include <linux/seq_buf.h>
 #include <linux/timex.h>
 #include <linux/timekeeping.h>
 
@@ -419,23 +420,24 @@ 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",
+       struct seq_buf s;
+
+       seq_buf_init(&s, analog->name, sizeof(analog->name));
+       seq_buf_printf(&s, "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));
+               seq_buf_printf(&s, " %d-hat",
+                              hweight16(analog->mask & ANALOG_HATS_ALL));
 
        if (analog->mask & ANALOG_HAT_FCS)
-               strlcat(analog->name, " FCS", sizeof(analog->name));
+               seq_buf_printf(&s, " FCS");
        if (analog->mask & ANALOG_ANY_CHF)
-               strlcat(analog->name, (analog->mask & ANALOG_SAITEK) ? " 
Saitek" : " CHF",
-                       sizeof(analog->name));
+               seq_buf_printf(&s, (analog->mask & ANALOG_SAITEK) ? " Saitek" : 
" CHF");
 
-       strlcat(analog->name, (analog->mask & ANALOG_GAMEPAD) ? " gamepad": " 
joystick",
-               sizeof(analog->name));
+       seq_buf_printf(&s, (analog->mask & ANALOG_GAMEPAD) ? " gamepad": " 
joystick");
 }
 
 /*
-- 
2.29.2