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

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Message-Id: <20120522134558.49255899.akpm@linux-foundation.org>
Date:	Tue, 22 May 2012 13:45:58 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
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 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.

> This hasn't been extensively tested.  Pretty much compile and
> boot tested along with Christoph's test case:
> 
> 	http://marc.info/?l=linux-mm&m=133728900729735

That isn't my favoritest ever changelog text :(
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