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Date:   Wed, 13 Sep 2023 00:07:21 +0000
Mime-Version: 1.0
Message-ID: <20230913-strncpy-drivers-cpufreq-cpufreq-c-v1-1-f1608bfeff63@google.com>
Subject: [PATCH] cpufreq: refactor deprecated strncpy
From:   Justin Stitt <justinstitt@google.com>
To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Viresh Kumar <viresh.kumar@linaro.org>
Cc:     linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
Content-Type: text/plain; charset="utf-8"
Precedence: bulk

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

We should prefer more robust and less ambiguous string interfaces.

Both `policy->last_governor` and `default_governor` are expected to be
NUL-terminated which is shown by their heavy usage with other string
apis like `strcmp`.

A suitable replacement is `strscpy` [2] due to the fact that it guarantees
NUL-termination on the destination buffer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested
---
 drivers/cpufreq/cpufreq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 50bbc969ffe5..3eb851a03fce 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1607,7 +1607,7 @@ static void __cpufreq_offline(unsigned int cpu, struct cpufreq_policy *policy)
 	}
 
 	if (has_target())
-		strncpy(policy->last_governor, policy->governor->name,
+		strscpy(policy->last_governor, policy->governor->name,
 			CPUFREQ_NAME_LEN);
 	else
 		policy->last_policy = policy->policy;
@@ -2951,7 +2951,7 @@ static int __init cpufreq_core_init(void)
 	BUG_ON(!cpufreq_global_kobject);
 
 	if (!strlen(default_governor))
-		strncpy(default_governor, gov->name, CPUFREQ_NAME_LEN);
+		strscpy(default_governor, gov->name, CPUFREQ_NAME_LEN);
 
 	return 0;
 }

---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230912-strncpy-drivers-cpufreq-cpufreq-c-1d800044b007

Best regards,
--
Justin Stitt <justinstitt@google.com>