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

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

Message-ID: <20160617123841.21b1a7e1@gandalf.local.home>
Date:	Fri, 17 Jun 2016 12:38:41 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	zhengjun.xing@...el.com
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH] tracing: Add *iter check for NULL

On Wed,  1 Jun 2016 16:31:10 +0800
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.

Could you show an example of this happening?

> 
> Signed-off-by: xingzhen <zhengjun.xing@...el.com>
> ---
>  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);

First, you can't place logic before a declaration. Not all compilers
will allow that.

Also, do we really want to error on this or just skip it? Because it
will miss out on all other trace_printks in the module.

-- Steve


>  		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);
>  }
>