Subject: Re: [PATCH v6] kptr_restrict for hiding kernel pointers
From: Joe Perches <joe@perches.com>
To: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        linux-security-module@vger.kernel.org, jmorris@namei.org,
        eric.dumazet@gmail.com, tgraf@infradead.org, eugeneteo@kernel.org,
        kees.cook@canonical.com, mingo@elte.hu, davem@davemloft.net,
        a.p.zijlstra@chello.nl, akpm@linux-foundation.org,
        eparis@parisplace.org
In-Reply-To: <1293058439.9820.317.camel@dan>
References: <1293058439.9820.317.camel@dan>
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Date: Wed, 22 Dec 2010 15:13:56 -0800
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On Wed, 2010-12-22 at 17:53 -0500, Dan Rosenberg wrote:
> Add the %pK printk format specifier and
> the /proc/sys/kernel/kptr_restrict sysctl.

trivial comments.

> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
[]
> @@ -201,6 +201,8 @@ extern int sscanf(const char *, const char *, ...)
>  extern int vsscanf(const char *, const char *, va_list)
>  	__attribute__ ((format (scanf, 2, 0)));
>  
> +extern int kptr_restrict;	/* for sysctl */

I think this extern should go into printk.h

> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
[]
> @@ -1035,6 +1038,30 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
>  		return buf + vsnprintf(buf, end - buf,
>  				       ((struct va_format *)ptr)->fmt,
>  				       *(((struct va_format *)ptr)->va));
> +	case 'K':
[]
> +		else if (!kptr_restrict)
> +			break;		/* %pK does not obscure pointers */
> +
> +		else if ((kptr_restrict != 2) &&
> +		    has_capability_noaudit(current, CAP_SYSLOG))
> +			break;		/* privileged apps expose pointers,
> +					   unless kptr_restrict is 2 */
> +

I think this more readable as:

		else if ((kptr_restrict == 0)) ||
			 (kptr_restrict == 1 &&
			  has_capability_noaudit(current, CAP_SYSLOG)))
			break;


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