linux-kernel - [PATCH] selftests/powerpc: Use snprintf to construct DSCR sysfs interface paths

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Date:   Thu, 28 Sep 2017 09:34:26 -0400
From:   Seth Forshee <seth.forshee@...onical.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Shuah Khan <shuah@...nel.org>
Cc:     Seth Forshee <seth.forshee@...onical.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] selftests/powerpc: Use snprintf to construct DSCR sysfs interface paths

Currently sprintf is used, and while paths should never exceed
the size of the buffer it is theoretically possible since
dirent.d_name is 256 bytes. As a result this trips
-Wformat-overflow, and since the test is built with -Wall -Werror
the causes the build to fail. Switch to using snprintf and skip
any paths which are too long for the filename buffer.

Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
---
 tools/testing/selftests/powerpc/dscr/dscr_sysfs_test.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/powerpc/dscr/dscr_sysfs_test.c b/tools/testing/selftests/powerpc/dscr/dscr_sysfs_test.c
index 17fb1b43c320..1899bd85121f 100644
--- a/tools/testing/selftests/powerpc/dscr/dscr_sysfs_test.c
+++ b/tools/testing/selftests/powerpc/dscr/dscr_sysfs_test.c
@@ -53,6 +53,8 @@ static int check_all_cpu_dscr_defaults(unsigned long val)
 	}
 
 	while ((dp = readdir(sysfs))) {
+		int len;
+
 		if (!(dp->d_type & DT_DIR))
 			continue;
 		if (!strcmp(dp->d_name, "cpuidle"))
@@ -60,7 +62,9 @@ static int check_all_cpu_dscr_defaults(unsigned long val)
 		if (!strstr(dp->d_name, "cpu"))
 			continue;
 
-		sprintf(file, "%s%s/dscr", CPU_PATH, dp->d_name);
+		len = snprintf(file, LEN_MAX, "%s%s/dscr", CPU_PATH, dp->d_name);
+		if (len >= LEN_MAX)
+			continue;
 		if (access(file, F_OK))
 			continue;
 
-- 
2.14.1