Re: [PATCH v2] tracing: Consider the NULL character when validating the event length

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

On Mon,  7 Oct 2024 15:47:24 +0100
Leo Yan <leo.yan@arm.com> wrote:

> strlen() returns a string length excluding the null byte. If the string
> length equals to the maximum buffer length, the buffer will have no
> space for the NULL terminating character.
> 
> This commit checks this condition and returns failure for it.
> 

Ah, good catch! The traceprobe_parse_event_name() requires
MAX_EVENT_NAME_LEN buffer.

----
/* @buf must has MAX_EVENT_NAME_LEN size */
int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
----

But the macro name is a bit confusing. We may need below and use it around.

#define EVENT_NAME_BUFSIZE (MAX_EVENT_NAME_LEN + 1)

Anyway, I think this fix is correct.

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

Thank you,

> Fixes: dec65d79fd26 ("tracing/probe: Check event name length correctly")
> Signed-off-by: Leo Yan <leo.yan@arm.com>
> ---
> 
> Changes from v1:
> Refined for condition checking (Steve).
> 
>  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..16a5e368e7b7 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 >= MAX_EVENT_NAME_LEN) {
>  		trace_probe_log_err(offset, EVENT_TOO_LONG);
>  		return -EINVAL;
>  	}
> -- 
> 2.34.1
> 


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