[PATCH] kallsyms: replace deprecated strncpy with strscpy

[PATCH] kallsyms: replace deprecated strncpy with strscpy

[Justin Stitt]

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@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.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@google.com>

Re: [PATCH] kallsyms: replace deprecated strncpy with strscpy

[Luis Chamberlain]

On Fri, Apr 12, 2024 at 06:53:47PM +0000, Justin Stitt wrote:
> 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Thanks! Queued up on modules-next.

  Luis