linux-kernel - Re: [PATCH] hugetlb: fix resv

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Message-ID: <4FBBFE49.4070409@linux.vnet.ibm.com>
Date:	Tue, 22 May 2012 13:59:53 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	cl@...ux.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	aarcange@...hat.com, kosaki.motohiro@...fujitsu.com,
	hughd@...gle.com, rientjes@...gle.com, adobriyan@...il.com,
	mel@....ul.ie
Subject: Re: [PATCH] hugetlb: fix resv_map leak in error path

On 05/22/2012 01:45 PM, Andrew Morton wrote:
> On Mon, 21 May 2012 13:28:14 -0700
> Dave Hansen <dave@...ux.vnet.ibm.com> wrote:
> 
>> When called for anonymous (non-shared) mappings,
>> hugetlb_reserve_pages() does a resv_map_alloc().  It depends on
>> code in hugetlbfs's vm_ops->close() to release that allocation.
>>
>> However, in the mmap() failure path, we do a plain unmap_region()
>> without the remove_vma() which actually calls vm_ops->close().
>>
>> This is a decent fix.  This leak could get reintroduced if
>> new code (say, after hugetlb_reserve_pages() in
>> hugetlbfs_file_mmap()) decides to return an error.  But, I think
>> it would have to unroll the reservation anyway.
> 
> How far back does this bug go?  The patch applies to 3.4 but gets
> rejects in 3.3 and earlier.

commit 17c9d12e126cb0de8d535dc1908c4819d712bc68
Date:   Wed Feb 11 16:34:16 2009 +0000

So, ~2.6.30.

I don't think it existed before that.  The code was there, but the
ordering made it OK.

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