linux-kernel - Re: [PATCH] x86, mm: get ASLR work for hugetlb mappings

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: <20131022175219.BB0E3E0090@blue.fi.intel.com>
Date:	Tue, 22 Oct 2013 20:52:19 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Nadia Yvette Chambers <nyc@...omorphy.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Matthew Wilcox <willy@...ux.intel.com>
Subject: Re: [PATCH] x86, mm: get ASLR work for hugetlb mappings

Dave Hansen wrote:
> On 10/22/2013 06:52 AM, Kirill A. Shutemov wrote:
> > Matthew noticed that hugetlb doesn't participate in ASLR on x86-64.
> > The reason is genereic hugetlb_get_unmapped_area() which is used on
> > x86-64. It doesn't support randomization and use bottom-up unmapped area
> > lookup, instead of usual top-down on x86-64.
> 
> I have to wonder if this was on purpose in order to keep the large and
> small mappings separate.  We don't *have* to keep them separate this, of
> course, but it makes me wonder.

I haven't seen any evidence that it's on purpose, but who knows...

In x86-specific hugetlb_get_unmapped_area() there's explicit check what is
mm->get_unmapped_area top-down or bottom-up, and doing the same.

> > x86 has arch-specific hugetlb_get_unmapped_area(), but it's used only on
> > x86-32.
> > 
> > Let's use arch-specific hugetlb_get_unmapped_area() on x86-64 too.
> > It fixes the issue and make hugetlb use top-down unmapped area lookup.
> 
> Shouldn't we fix the generic code instead of further specializing the
> x86 stuff?

For that we need to modify info.low_limit to mm->mmap_legacy_base (which
is x86 specific, no-go) or switch to top-down and set info.high_limit to
mm->mmap_base.

I don't know how it can affect other architectures.

> In any case, you probably also want to run this through: the
> libhugetlbfs tests:
> 
> http://sourceforge.net/p/libhugetlbfs/code/ci/master/tree/tests/

I've got the same fail list for upstream and patched kernel, so no
regression was found.

********** TEST SUMMARY  
*                      2M            
*                      32-bit 64-bit 
*     Total testcases:   107    110   
*             Skipped:     0      0   
*                PASS:    98    108   
*                FAIL:     2      2   
*    Killed by signal:     7      0   
*   Bad configuration:     0      0   
*       Expected FAIL:     0      0   
*     Unexpected PASS:     0      0   
* Strange test result:     0      0   
**********

-- 
 Kirill A. Shutemov
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/