linux-kernel - Re: [PATCH] tracing: Consider the NULL character when validating the event length

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Message-ID: <20241007102242.18d2636e@gandalf.local.home>
Date: Mon, 7 Oct 2024 10:22:42 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Leo Yan <leo.yan@....com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Dave.Martin@....com,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Consider the NULL character when validating
 the event length

On Mon,  7 Oct 2024 14:51:26 +0100
Leo Yan <leo.yan@....com> wrote:

> strlen() returns a string length excluding the null byte. This commit
> adds 1 to account for the NULL terminating character when checking if an
> event string is within the maximum length.
> 
> Fixes: dec65d79fd26 ("tracing/probe: Check event name length correctly")
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
>  kernel/trace/trace_probe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 39877c80d6cb..376ba56c3680 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -276,7 +276,7 @@ int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
>  		}
>  		trace_probe_log_err(offset, NO_EVENT_NAME);
>  		return -EINVAL;
> -	} else if (len > MAX_EVENT_NAME_LEN) {
> +	} else if (len + 1 > MAX_EVENT_NAME_LEN) {

Usually, the check is:

	} else if (len >= MAX_EVENT_NAME_LEN) {

Which is a better way to check max length.

-- Steve


>  		trace_probe_log_err(offset, EVENT_TOO_LONG);
>  		return -EINVAL;
>  	}