linux-kernel - Re: [PATCH] kernel/printk/printk.c: check_syslog

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Date:	Sun, 24 May 2015 19:09:35 +0300
From:	Vasily Averin <vvs@...tuozzo.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Vasily Averin <vvs@...n.com>
CC:	linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
	Josh Boyer <jwboyer@...hat.com>, Eric Paris <eparis@...hat.com>
Subject: Re: [PATCH] kernel/printk/printk.c: check_syslog_permissions() cleanup

On 15.05.2015 01:01, Andrew Morton wrote:
> On Sun, 10 May 2015 09:35:53 +0300 Vasily Averin <vvs@...n.com> wrote:
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -484,11 +484,11 @@ int check_syslog_permissions(int type, bool from_file)
>>  	 * already done the capabilities checks at open time.
>>  	 */
>>  	if (from_file && type != SYSLOG_ACTION_OPEN)
>> -		return 0;
>> +		goto ok;
> 
> This seems wrong - we should only call security_syslog() for opens?

No I think my version is correct.
Currently security hook _is_ called in this situation:
from_file is set in /proc/kmsg handlers only, 
they use do_syslog() and call security_syslog() directly
after check_syslog_permissions() call.

My patch forces check_syslog_permissions() to call security hook in all cases,
that allows to remove extra security_syslog() call from do_syslog().

I've changed patch comment and going to resend new patch version soon.
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