linux-kernel - Re: [PATCH] mm: remap_file_pages: grab file ref to prevent race while mmaping

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Message-ID: <20140514091546.GA29388@node.dhcp.inet.fi>
Date:	Wed, 14 May 2014 12:15:46 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	linux-mm@...ck.org, kirill.shutemov@...ux.intel.com,
	davej@...hat.com, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, peterz@...radead.org, mingo@...nel.org
Subject: Re: [PATCH] mm: remap_file_pages: grab file ref to prevent race
 while mmaping

On Tue, May 13, 2014 at 11:35:42PM -0400, Sasha Levin wrote:
> A file reference should be held while a file is mmaped, otherwise it might
> be freed while being used.
> 
> Suggested-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>

Sorry, again. :-/

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

> ---
>  mm/mmap.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 2a0e0a8..da3c212 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2593,6 +2593,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  	struct vm_area_struct *vma;
>  	unsigned long populate = 0;
>  	unsigned long ret = -EINVAL;
> +	struct file *file;
>  
>  	pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. "
>  			"See Documentation/vm/remap_file_pages.txt.\n",
> @@ -2636,8 +2637,10 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  		munlock_vma_pages_range(vma, start, start + size);
>  	}
>  
> +	file = get_file(vma->vm_file);
>  	ret = do_mmap_pgoff(vma->vm_file, start, size,
>  			prot, flags, pgoff, &populate);
> +	fput(file);
>  out:
>  	up_write(&mm->mmap_sem);
>  	if (populate)
> -- 
> 1.7.10.4
> 
> --
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-- 
 Kirill A. Shutemov
--
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