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Date: Mon, 29 Apr 2024 20:50:30 +0000
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Message-ID: <20240429-strncpy-kernel-power-hibernate-c-v1-1-8688f492d3e6@google.com>
Subject: [PATCH] PM: hibernate: replace deprecated strncpy with strscpy
From: Justin Stitt <justinstitt@google.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>, Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-hardening@vger.kernel.org, Justin Stitt <justinstitt@google.com>
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strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

This kernel config option is simply assigned with the resume_file
buffer. It should be NUL-terminated but not necessarily NUL-padded as
per its further usage with other string apis:
|	static int __init find_resume_device(void)
|	{
|		if (!strlen(resume_file))
|			return -ENOENT;
|
|		pm_pr_dbg("Checking hibernation image partition %s\n", resume_file);

Use strscpy [2] as it guarantees NUL-termination on the destination
buffer. Specifically, use the new 2-argument version of strscpy()
introduced in Commit e6584c3964f2f ("string: Allow 2-argument
strscpy()").

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 only.

Found with: $ rg "strncpy\("
---
 kernel/power/hibernate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 43b1a82e800c..0a213f69a9e4 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1361,7 +1361,7 @@ static int __init resume_setup(char *str)
 	if (noresume)
 		return 1;
 
-	strncpy(resume_file, str, 255);
+	strscpy(resume_file, str);
 	return 1;
 }
 

---
base-commit: d7ad0581567927c433918bb5f06f3d29f89807d3
change-id: 20240412-strncpy-kernel-power-hibernate-c-77985696443c

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