linux-kernel - Re: [PATCH -next v2] ftrace: Fix potential warning in trace_printk_seq during ftrace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <84a2f916-47c5-4c6f-9d36-771f60db35fc@huaweicloud.com>
Date: Fri, 22 Aug 2025 09:26:22 +0800
From: Tengda Wu <wutengda@...weicloud.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Ingo Molnar <mingo@...e.hu>, linux-trace-kernel@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v2] ftrace: Fix potential warning in
 trace_printk_seq during ftrace_dump



On 2025/8/21 23:05, Steven Rostedt wrote:
> On Thu, 21 Aug 2025 02:11:20 +0000
> Tengda Wu <wutengda@...weicloud.com> wrote:
> 
>  tested this and was writing the change log for the pull request when I
> realized an issue.
> 
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index 4283ed4e8f59..b4cec22753ea 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -10617,6 +10617,7 @@ static void ftrace_dump_one(struct trace_array *tr, enum ftrace_dump_mode dump_m
>>  	 */
>>  
>>  	while (!trace_empty(&iter)) {
>> +		void *ent;
>>  
>>  		if (!cnt)
>>  			printk(KERN_TRACE "---------------------------------\n");
>> @@ -10625,17 +10626,18 @@ static void ftrace_dump_one(struct trace_array *tr, enum ftrace_dump_mode dump_m
>>  
>>  		trace_iterator_reset(&iter);
>>  		iter.iter_flags |= TRACE_FILE_LAT_FMT;
>> +		ent = trace_find_next_entry_inc(&iter);
>>  
>> -		if (trace_find_next_entry_inc(&iter) != NULL) {
>> +		if (ent) {
> 
> Why do we need "ent"?
> 
> 
>>  			int ret;
>>  
>>  			ret = print_trace_line(&iter);
>>  			if (ret != TRACE_TYPE_NO_CONSUME)
>>  				trace_consume(&iter);
>> +
>> +			trace_printk_seq(&iter.seq);
> 
> Isn't just moving trace_printk_seq() enough?
> 
> The code is no different with or without the "ent" as "ent" is not used in
> the if block.
> 
> -- Steve

I apologize, as this is a trace left over from the initial patch modification
process. While working with the original code, I added an `if (ent)` branch
directly to trace_printk_seq and later realized it could be merged with the
previous `if (ent)` branch. However, I forgot to remove the now-redundant ent
after the merge. 

I will correct this immediately and resend a new version.

-- Tengda



> 
> 
>>  		}
>>  		touch_nmi_watchdog();
>> -
>> -		trace_printk_seq(&iter.seq);
>>  	}
>>  
>>  	if (!cnt)