tracing: Always use memcpy() in histogram add_to_key()

[PATCH] tracing: Always use memcpy() in histogram add_to_key()

Posted by Steven Rostedt 10 months, 1 week ago

From: Steven Rostedt <rostedt@goodmis.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@goodmis.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
-- 
2.47.2

Re: [PATCH] tracing: Always use memcpy() in histogram add_to_key()

Posted by Tom Zanussi 10 months ago

Hi Steve,

On Thu, 2025-04-03 at 21:06 -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.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@goodmis.org>

Looks good, thanks.

Reviewed-by: Tom Zanussi <zanussi@kernel.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

Re: [PATCH] tracing: Always use memcpy() in histogram add_to_key()

Posted by Masami Hiramatsu (Google) 10 months, 1 week ago

On Thu, 3 Apr 2025 21:06:37 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: Steven Rostedt <rostedt@goodmis.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.
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thank you,

> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.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
> -- 
> 2.47.2
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>