linux-kernel - Re: [PATCH 1/5] fs/hugetlbfs/inode.c: Fix pgoff alignment checking on 32-bit

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Date:	Tue, 19 Jul 2011 14:43:49 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	"linux-mm@...ck.org" <linux-mm@...ck.org>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	david@...son.dropbear.id.au, galak@...nel.crashing.org,
	Becky Bruce <beckyb@...nel.crashing.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/5] fs/hugetlbfs/inode.c: Fix pgoff alignment checking
 on 32-bit

Andrew, Anybody ? Can I have an -mm ack for this ?

Cheers,
Ben.

On Tue, 2011-06-28 at 14:54 -0500, Becky Bruce wrote:
> From: Becky Bruce <beckyb@...nel.crashing.org>
> 
> This:
> 
> vma->vm_pgoff & ~(huge_page_mask(h) >> PAGE_SHIFT)
> 
> is incorrect on 32-bit.  It causes us to & the pgoff with
> something that looks like this (for a 4m hugepage): 0xfff003ff.
> The mask should be flipped and *then* shifted, to give you
> 0x0000_03fff.
> 
> Signed-off-by: Becky Bruce <beckyb@...nel.crashing.org>
> ---
>  fs/hugetlbfs/inode.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 7aafeb8..537a209 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -94,7 +94,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
>  	vma->vm_flags |= VM_HUGETLB | VM_RESERVED;
>  	vma->vm_ops = &hugetlb_vm_ops;
>  
> -	if (vma->vm_pgoff & ~(huge_page_mask(h) >> PAGE_SHIFT))
> +	if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
>  		return -EINVAL;
>  
>  	vma_len = (loff_t)(vma->vm_end - vma->vm_start);


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