linux-kernel - Re: [PATCH 1/3] revoke: misc fixes

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Date:	Fri, 16 Mar 2007 18:21:48 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Pekka J Enberg <penberg@...helsinki.fi>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] revoke: misc fixes

Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@...helsinki.fi>
> 
> This is a rollup patch of the following fixes to address some of Andrew's
> review comments:
> 
>   - Fix return value type of system calls to long
>   - Add comment for vma->vm_flag barrier
>   - No need for GFP_NOFS for inode allocation, use GFP_KERNEL instead
>   - Remove unnecessary line break before EXPORT_SYMBOL
> 
> Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
> ---
>  fs/revoke.c              |    9 +++++----
>  include/linux/syscalls.h |    4 ++--
>  2 files changed, 7 insertions(+), 6 deletions(-)
> 
> Index: uml-2.6/fs/revoke.c
> ===================================================================
> --- uml-2.6.orig/fs/revoke.c	2007-03-16 08:58:31.000000000 +0200
> +++ uml-2.6/fs/revoke.c	2007-03-16 09:00:37.000000000 +0200
> @@ -167,7 +167,9 @@ static int revoke_vma(struct vm_area_str
>  	end_addr = vma->vm_end;
>  
>  	/*
> - 	 * Not holding ->mmap_sem here.
> + 	 * Not holding ->mmap_sem here but we must watch out for page
> + 	 * faults and after the shared mappings have been taken down
> + 	 * and sys_mmap() trying to remap the revoked range.
>  	 */
>  	vma->vm_flags |= VM_REVOKED;
>  	smp_mb();
> @@ -455,7 +457,7 @@ 	int err = 0;

You're still modifying vm_flags without down_write mmap_sem, so this will
corrupt vm_flags.

-- 
SUSE Labs, Novell Inc.
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