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From: Vasiliy Kulikov <segoon@openwall.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	kernel-hardening@lists.openwall.com,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC] x86, mm: start mmap allocation for libs from low addresses
Date: Sat, 13 Aug 2011 10:26:14 +0400	[thread overview]
Message-ID: <20110813062614.GD3851@albatros> (raw)
In-Reply-To: <ccea406f-62be-4344-8036-a1b092937fe9@email.android.com>

On Fri, Aug 12, 2011 at 18:19 -0500, H. Peter Anvin wrote:
> This also greatly reduces the address space available for randomization,
> and may get in the way of the default brk.  Is this a net win or lose?

If the executable image is not randomized and is located out of
ASCII-armor, then yes, such allocation doesn't help much.

>  Also, this zero byte is going to be at the last address, which means it might not help.  How about addresses of the form 0xAA00B000 instead?  The last bits are always 000 for a page address, of course...

It leaves only 64kb of library protected, which is useless for most of
programs.

Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments

WARNING: multiple messages have this Message-ID (diff)
From: Vasiliy Kulikov <segoon@openwall.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	kernel-hardening@lists.openwall.com,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC] x86, mm: start mmap allocation for libs from low addresses
Date: Sat, 13 Aug 2011 10:26:14 +0400	[thread overview]
Message-ID: <20110813062614.GD3851@albatros> (raw)
In-Reply-To: <ccea406f-62be-4344-8036-a1b092937fe9@email.android.com>

On Fri, Aug 12, 2011 at 18:19 -0500, H. Peter Anvin wrote:
> This also greatly reduces the address space available for randomization,
> and may get in the way of the default brk.  Is this a net win or lose?

If the executable image is not randomized and is located out of
ASCII-armor, then yes, such allocation doesn't help much.

>  Also, this zero byte is going to be at the last address, which means it might not help.  How about addresses of the form 0xAA00B000 instead?  The last bits are always 000 for a page address, of course...

It leaves only 64kb of library protected, which is useless for most of
programs.

Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments

--
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WARNING: multiple messages have this Message-ID (diff)
From: Vasiliy Kulikov <segoon@openwall.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	kernel-hardening@lists.openwall.com,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [kernel-hardening] Re: [RFC] x86, mm: start mmap allocation for libs from low addresses
Date: Sat, 13 Aug 2011 10:26:14 +0400	[thread overview]
Message-ID: <20110813062614.GD3851@albatros> (raw)
In-Reply-To: <ccea406f-62be-4344-8036-a1b092937fe9@email.android.com>

On Fri, Aug 12, 2011 at 18:19 -0500, H. Peter Anvin wrote:
> This also greatly reduces the address space available for randomization,
> and may get in the way of the default brk.  Is this a net win or lose?

If the executable image is not randomized and is located out of
ASCII-armor, then yes, such allocation doesn't help much.

>  Also, this zero byte is going to be at the last address, which means it might not help.  How about addresses of the form 0xAA00B000 instead?  The last bits are always 000 for a page address, of course...

It leaves only 64kb of library protected, which is useless for most of
programs.

Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments

  reply	other threads:[~2011-08-13  6:26 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-12 10:29 [RFC] x86, mm: start mmap allocation for libs from low addresses Vasiliy Kulikov
2011-08-12 10:29 ` [kernel-hardening] " Vasiliy Kulikov
2011-08-12 10:29 ` Vasiliy Kulikov
2011-08-12 10:58 ` [kernel-hardening] " Solar Designer
2011-08-12 11:05   ` Vasiliy Kulikov
2011-08-25 17:19   ` Vasiliy Kulikov
2011-08-25 17:39     ` Solar Designer
2011-09-02 18:29     ` Solar Designer
2011-09-03 11:18       ` Vasiliy Kulikov
2011-09-03 23:57         ` Solar Designer
2011-09-05 12:46           ` Vasiliy Kulikov
2011-09-06  5:05             ` Solar Designer
2011-09-07  9:09               ` Vasiliy Kulikov
2011-09-07  9:30                 ` Solar Designer
2011-09-07  9:34                   ` Vasiliy Kulikov
2011-09-07  9:43                     ` Solar Designer
2011-09-07  9:55                       ` Vasiliy Kulikov
2011-09-07 10:16                         ` Solar Designer
2011-09-07 11:01                           ` Vasiliy Kulikov
2011-09-02 23:34     ` Solar Designer
2011-09-03 12:12       ` Vasiliy Kulikov
2011-09-03 23:40         ` Solar Designer
2011-09-04  7:21         ` Vasiliy Kulikov
2011-08-12 23:19 ` H. Peter Anvin
2011-08-12 23:19   ` [kernel-hardening] " H. Peter Anvin
2011-08-12 23:19   ` H. Peter Anvin
2011-08-13  6:26   ` Vasiliy Kulikov [this message]
2011-08-13  6:26     ` [kernel-hardening] " Vasiliy Kulikov
2011-08-13  6:26     ` Vasiliy Kulikov
2011-08-16  9:05   ` Vasiliy Kulikov
2011-08-16  9:05     ` [kernel-hardening] " Vasiliy Kulikov
2011-08-16  9:05     ` Vasiliy Kulikov
2011-08-22 10:17     ` Vasiliy Kulikov
2011-08-22 10:17       ` [kernel-hardening] " Vasiliy Kulikov
2011-08-22 10:17       ` Vasiliy Kulikov
2011-08-22 17:24       ` H. Peter Anvin
2011-08-22 17:24         ` [kernel-hardening] " H. Peter Anvin
2011-08-22 17:24         ` H. Peter Anvin
2011-08-22 20:14         ` Vasiliy Kulikov
2011-08-22 20:14           ` [kernel-hardening] " Vasiliy Kulikov
2011-08-22 20:14           ` Vasiliy Kulikov
2011-08-22 20:17           ` H. Peter Anvin
2011-08-22 20:17             ` [kernel-hardening] " H. Peter Anvin
2011-08-22 20:17             ` H. Peter Anvin
2011-08-23  6:41             ` Vasiliy Kulikov
2011-08-23  6:41               ` [kernel-hardening] " Vasiliy Kulikov
2011-08-23  6:41               ` Vasiliy Kulikov

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