linux-kernel - Re: [PATCH] tracing: Fix out-of-range read in trace_stack

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Date:   Sun, 30 Jun 2019 18:03:59 +0900
From:   Eiichi Tsukata <devel@...ukata.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] tracing: Fix out-of-range read in trace_stack_print()



On 2019/06/15 5:31, Steven Rostedt wrote:
...

> 
>>
>> Fixes: 4a9bd3f134dec ("tracing: Have dynamic size event stack traces")
> 
> Actually it fixes:
> 
>  4285f2fcef80 ("tracing: Remove the ULONG_MAX stack trace hackery")
> 
> Because before that, a ULONG_MAX was inserted into the buffer.
> 
> -- Steve

Thank you for the advice.
Now there is no ULONG_MAX marker, so I should have fixed it by just
removing `*p != ULONG_MAX` check, right?


Thanks

Eiichi

> 
>> Signed-off-by: Eiichi Tsukata <devel@...ukata.com>
>> ---
>>  kernel/trace/trace_output.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
>> index 54373d93e251..ba751f993c3b 100644
>> --- a/kernel/trace/trace_output.c
>> +++ b/kernel/trace/trace_output.c
>> @@ -1057,7 +1057,7 @@ static enum print_line_t trace_stack_print(struct trace_iterator *iter,
>>  
>>  	trace_seq_puts(s, "<stack trace>\n");
>>  
>> -	for (p = field->caller; p && *p != ULONG_MAX && p < end; p++) {
>> +	for (p = field->caller; p && p < end && *p != ULONG_MAX; p++) {
>>  
>>  		if (trace_seq_has_overflowed(s))
>>  			break;
>