linux-hardening - [PATCH] kallsyms: replace deprecated strncpy with strscpy

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Message-ID: <20240412-strncpy-kernel-module-kallsyms-c-v1-1-ba3f0fc16163@google.com>
Date: Fri, 12 Apr 2024 18:53:47 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Luis Chamberlain <mcgrof@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>
Cc: linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] kallsyms: replace deprecated strncpy with strscpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces. The goal is to remove its use completely [2].

namebuf is eventually cleaned of any trailing llvm suffixes using
strstr(). This hints that namebuf should be NUL-terminated.

static void cleanup_symbol_name(char *s)
{
	char *res;
	...
	res = strstr(s, ".llvm.");
	...
}

Due to this, use strscpy() over strncpy() as it guarantees
NUL-termination on the destination buffer. Drop the -1 from the length
calculation as it is no longer needed to ensure NUL-termination.

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
Link: https://github.com/KSPP/linux/issues/90 [2]
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
---
 kernel/module/kallsyms.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index ef73ae7c8909..62fb57bb9f16 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -348,7 +348,7 @@ const char *module_address_lookup(unsigned long addr,
 	}
 	/* Make a copy in here where it's safe */
 	if (ret) {
-		strncpy(namebuf, ret, KSYM_NAME_LEN - 1);
+		strscpy(namebuf, ret, KSYM_NAME_LEN);
 		ret = namebuf;
 	}
 	preempt_enable();

---
base-commit: d7ad0581567927c433918bb5f06f3d29f89807d3
change-id: 20240412-strncpy-kernel-module-kallsyms-c-8539c5e7bf57

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