[PATCH 8/8] x86: intel-mid: fix a format string overflow warning

From: Arnd Bergmann
Date: Wed Jul 19 2017 - 08:56:51 EST


We have space for exactly three characters for the index in "max7315_%d_base",
but as gcc points out having more would cause an string overflow:

arch/x86/platform/intel-mid/device_libs/platform_max7315.c: In function 'max7315_platform_data':
arch/x86/platform/intel-mid/device_libs/platform_max7315.c:41:26: error: '%d' directive writing between 1 and 11 bytes into a region of size 9 [-Werror=format-overflow=]
sprintf(base_pin_name, "max7315_%d_base", nr);
^~~~~~~~~~~~~~~~~
arch/x86/platform/intel-mid/device_libs/platform_max7315.c:41:26: note: directive argument in the range [-2147483647, 2147483647]
arch/x86/platform/intel-mid/device_libs/platform_max7315.c:41:3: note: 'sprintf' output between 15 and 25 bytes into a destination of size 17
sprintf(base_pin_name, "max7315_%d_base", nr);

This makes it use an snprintf() to truncate the string if that happened
rather than overflowing the stack. In practice, this is safe, because
there won't be a large number of max7315 devices in the systems, and
both the format and the length are defined by the firmware interface.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
Originally submitted on July 14, this is the same patch with slightly
improved changelog.
---
arch/x86/platform/intel-mid/device_libs/platform_max7315.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/intel-mid/device_libs/platform_max7315.c b/arch/x86/platform/intel-mid/device_libs/platform_max7315.c
index 6e075afa7877..58337b2bc682 100644
--- a/arch/x86/platform/intel-mid/device_libs/platform_max7315.c
+++ b/arch/x86/platform/intel-mid/device_libs/platform_max7315.c
@@ -38,8 +38,10 @@ static void __init *max7315_platform_data(void *info)
*/
strcpy(i2c_info->type, "max7315");
if (nr++) {
- sprintf(base_pin_name, "max7315_%d_base", nr);
- sprintf(intr_pin_name, "max7315_%d_int", nr);
+ snprintf(base_pin_name, sizeof(base_pin_name),
+ "max7315_%d_base", nr);
+ snprintf(intr_pin_name, sizeof(intr_pin_name),
+ "max7315_%d_int", nr);
} else {
strcpy(base_pin_name, "max7315_base");
strcpy(intr_pin_name, "max7315_int");
--
2.9.0