linux-kernel - Re: [PATCH] tracing: Add *iter check for NULL

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Message-ID: <CADWwUUbXzWYRQYCfqNLmz5RQUHZf4qWjbDQv8_Y2PJzzZRD0=A@mail.gmail.com>
Date:	Fri, 3 Jun 2016 00:41:25 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	zhengjun.xing@...el.com
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: Add *iter check for NULL

Hello,

On Wed, Jun 1, 2016 at 5:31 PM,  <zhengjun.xing@...el.com> wrote:
> From: xingzhen <zhengjun.xing@...el.com>
>
> 3debb0a9ddb adding a "__used" to the variable in the
> __trace_printk_fmt section. Sometimes it will cause
> *iter to be NULL, then strcmp in lookup_format and
> strcpy in hold_module_trace_bprintk_format will panic.
>
> Signed-off-by: xingzhen <zhengjun.xing@...el.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


> ---
>  kernel/trace/trace_printk.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
> index f96f038..82ecfb5 100644
> --- a/kernel/trace/trace_printk.c
> +++ b/kernel/trace/trace_printk.c
> @@ -55,6 +55,8 @@ void hold_module_trace_bprintk_format(const char **start, const char **end)
>
>         mutex_lock(&btrace_mutex);
>         for (iter = start; iter < end; iter++) {
> +               if (!*iter)
> +                       goto err;
>                 struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
>                 if (tb_fmt) {
>                         *iter = tb_fmt->fmt;
> @@ -75,6 +77,7 @@ void hold_module_trace_bprintk_format(const char **start, const char **end)
>                 *iter = fmt;
>
>         }
> +err:
>         mutex_unlock(&btrace_mutex);
>  }
>
> --
> 1.9.1
>