linux-kernel - Re: [PATCH] ftrace: Modify parameter transfer type

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Date:   Tue, 30 Mar 2021 09:39:16 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: Modify parameter transfer type

On Tue, 30 Mar 2021 18:02:26 +0800
Jiapeng Chong <jiapeng.chong@...ux.alibaba.com> wrote:

> Fix the following whitescan warning:
> 
> "order" is passed to a parameter that cannot be negative.
> 
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  kernel/trace/ftrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index b7e29db..bd42e86 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6811,7 +6811,7 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
>  		if (!pg->index) {
>  			*last_pg = pg->next;
>  			order = get_count_order(pg->size / ENTRIES_PER_PAGE);
> -			free_pages((unsigned long)pg->records, order);
> +			free_pages((unsigned long)pg->records, (unsigned int)order);

NAK!

This "fix" actually makes the problem worse, and hides a possible bug.

-- Steve


>  			ftrace_number_of_pages -= 1 << order;
>  			ftrace_number_of_groups--;
>  			kfree(pg);