[PATCH] commands: hwclock: replace strncpy with strlcpy

[PATCH] commands: hwclock: replace strncpy with strlcpy

[Jules Maselbas]

strncpy could leave the rtc_name buffer not nul-terminated, strlcpy will
always nul-terminate the dst buffer.
Also replace the hardcoded size with sizeof(rtc_name)

Signed-off-by: Jules Maselbas <jmaselbas@zdiv.net>
---
 commands/hwclock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/commands/hwclock.c b/commands/hwclock.c
index c594e070ac..33829e4118 100644
--- a/commands/hwclock.c
+++ b/commands/hwclock.c
@@ -95,7 +95,7 @@ static int do_hwclock(int argc, char *argv[])
 
 		switch (opt) {
 		case 'f':
-			strncpy(rtc_name, optarg, 16);
+			strlcpy(rtc_name, optarg, sizeof(rtc_name));
 			break;
 		case 's':
 			memset(&stm, 0, sizeof(stm));
-- 
2.48.1

Re: [PATCH] commands: hwclock: replace strncpy with strlcpy

[Sascha Hauer]

Hi Jules,

On Fri, Mar 14, 2025 at 10:33:44PM +0100, Jules Maselbas wrote:
> strncpy could leave the rtc_name buffer not nul-terminated, strlcpy will
> always nul-terminate the dst buffer.
> Also replace the hardcoded size with sizeof(rtc_name)
> 
> Signed-off-by: Jules Maselbas <jmaselbas@zdiv.net>
> ---
>  commands/hwclock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/commands/hwclock.c b/commands/hwclock.c
> index c594e070ac..33829e4118 100644
> --- a/commands/hwclock.c
> +++ b/commands/hwclock.c
> @@ -95,7 +95,7 @@ static int do_hwclock(int argc, char *argv[])
>  
>  		switch (opt) {
>  		case 'f':
> -			strncpy(rtc_name, optarg, 16);
> +			strlcpy(rtc_name, optarg, sizeof(rtc_name));
>  			break;

rtc_name is an array for no good reason. Can we just do a

const char *rtc_name = "rtc0";

		case 'f':
			rtc_name = optarg;

Sascha

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