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

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Message-ID: <fdad61fc-c3cf-43b4-a049-b428ea89013f@arm.com>
Date: Mon, 7 Oct 2024 15:33:47 +0100
From: Leo Yan <leo.yan@....com>
To: Steven Rostedt <rostedt@...dmis.org>
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 10/7/24 15:22, Steven Rostedt wrote:
> Warning: EXTERNAL SENDER, use caution when opening links or attachments.
> 
> 
> 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.

Will update. Thanks for suggestion.

Leo