linux-kernel - [tip:x86/urgent] x86/platform/intel-mid: Fix a format string overflow warning

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Date:   Thu, 20 Jul 2017 03:27:01 -0700
From:   tip-bot for Arnd Bergmann <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, arnd@...db.de, hpa@...or.com,
        mingo@...nel.org, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: [tip:x86/urgent] x86/platform/intel-mid: Fix a format string
 overflow warning

Commit-ID:  0bc73048d7baecf94117d1a948853a627e6ba5c8
Gitweb:     http://git.kernel.org/tip/0bc73048d7baecf94117d1a948853a627e6ba5c8
Author:     Arnd Bergmann <arnd@...db.de>
AuthorDate: Wed, 19 Jul 2017 14:53:06 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 20 Jul 2017 10:46:25 +0200

x86/platform/intel-mid: Fix a format string overflow warning

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@...db.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20170719125310.2487451-9-arnd@arndb.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 6e075af..58337b2 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");