linux-hardening - Re: [PATCH] tracing: Always use memcpy() in histogram add_to

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Message-ID: <d37227b12b2fa46dfe4d50f11c428040ed79a076.camel@kernel.org>
Date: Tue, 08 Apr 2025 14:32:50 -0500
From: Tom Zanussi <zanussi@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>, LKML
 <linux-kernel@...r.kernel.org>,  Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
	 <mathieu.desnoyers@...icios.com>, Kees Cook <keescook@...omium.org>, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] tracing: Always use memcpy() in histogram add_to_key()

Hi Steve,

On Thu, 2025-04-03 at 21:06 -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@...dmis.org>
> 
> The add_to_key() function tests if the key is a string or some data. If
> it's a string it does some further calculations of the string size (still
> truncating it to the max size it can be), and calls strncpy().
> 
> If the key isn't as string it calls memcpy(). The interesting point is
> that both use the exact same parameters:
> 
>                 strncpy(compound_key + key_field->offset, (char *)key, size);
>         } else
>                 memcpy(compound_key + key_field->offset, key, size);
> 
> As strncpy() is being used simply as a memcpy() for a string, and since
> strncpy() is deprecated, just call memcpy() for both memory and string
> keys.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Looks good, thanks.

Reviewed-by: Tom Zanussi <zanussi@...nel.org>

> ---
>  kernel/trace/trace_events_hist.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index c1ea6aaac182..4258324219ca 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -5224,10 +5224,8 @@ static inline void add_to_key(char *compound_key, void *key,
>  		/* ensure NULL-termination */
>  		if (size > key_field->size - 1)
>  			size = key_field->size - 1;
> -
> -		strncpy(compound_key + key_field->offset, (char *)key, size);
> -	} else
> -		memcpy(compound_key + key_field->offset, key, size);
> +	}
> +	memcpy(compound_key + key_field->offset, key, size);
>  }
>  
>  static void