linux-kernel - Re: [PATCH] sys_remap_file_pages: fix ->vm

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Message-ID: <20080130172646.GA2355@tv-sign.ru>
Date:	Wed, 30 Jan 2008 20:26:46 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Miklos Szeredi <mszeredi@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	William Lee Irwin III <wli@...omorphy.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	stable@...nel.org, Matt Helsley <matthltc@...ibm.com>
Subject: Re: [PATCH] sys_remap_file_pages: fix ->vm_file accounting

On 01/30, Miklos Szeredi wrote:
> 
> On Wed, 2008-01-30 at 17:20 +0300, Oleg Nesterov wrote:
> > Fix ->vm_file accounting, mmap_region() may do do_munmap().
> 
> There's a small problem with the patch: the vma itself is freed at
> unmap, so the fput(vma->vm_file) may crash.  Here's an updated patch.

Ah, indeed, thanks!


Offtopic. I noticed this problem while looking at this patch:

	http://marc.info/?l=linux-mm-commits&m=120141116911711

So this (the old vma could be removed before we create the new mapping)
means that the patch above has another problem: if we are remapping the
whole VM_EXECUTABLE vma, removed_exe_file_vma() can clear ->exe_file
while it shouldn't (Matt Helsley cc'ed).

Oleg.

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