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Groups > linux.kernel > #1353396

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

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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@rasmusvillemoes.dk>
---
 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

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[RFC 0/7] eliminate snprintf with overlapping src and dst Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-08 21:50 +0100
  [RFC 5/7] wlcore: avoid fragile snprintf use Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-08 21:50 +0100
    Re: [RFC 5/7] wlcore: avoid fragile snprintf use Kalle Valo <kvalo@codeaurora.org> - 2016-03-09 12:50 +0100
  [RFC 3/7] leds: avoid fragile sprintf use Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-08 21:50 +0100
  [RFC 4/7] drivers/media/pci/zoran: avoid fragile snprintf use Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-08 21:50 +0100
  [RFC 2/7] Input: joystick - avoid fragile snprintf use Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-08 21:50 +0100
    Re: [RFC 2/7] Input: joystick - avoid fragile snprintf use Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-03-09 07:50 +0100
  [RFC 1/7] drm/amdkfd: avoid fragile and inefficient snprintf use Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-08 21:50 +0100
    Re: [RFC 1/7] drm/amdkfd: avoid fragile and inefficient snprintf use Oded Gabbay <oded.gabbay@gmail.com> - 2016-03-14 15:40 +0100
      Re: [RFC 1/7] drm/amdkfd: avoid fragile and inefficient snprintf use Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-14 20:20 +0100
  Re: [RFC 0/7] eliminate snprintf with overlapping src and dst Kees Cook <keescook@chromium.org> - 2016-03-09 00:10 +0100
  Re: [RFC 0/7] eliminate snprintf with overlapping src and dst Kees Cook <keescook@chromium.org> - 2016-03-09 00:20 +0100
  Re: [RFC 0/7] eliminate snprintf with overlapping src and dst Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-03-09 08:00 +0100
  Re: [RFC 0/7] eliminate snprintf with overlapping src and dst Andrew Morton <akpm@linux-foundation.org> - 2016-03-09 21:50 +0100
    Re: [RFC 0/7] eliminate snprintf with overlapping src and dst Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2016-03-09 23:20 +0100
    Re: [RFC 0/7] eliminate snprintf with overlapping src and dst One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-03-10 15:10 +0100

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