From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Pekka J Enberg <penberg@cs.helsinki.fi>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] revoke: break cow for private mappings
Date: Wed, 28 Mar 2007 18:04:20 +1000 [thread overview]
Message-ID: <460A2184.8060207@yahoo.com.au> (raw)
In-Reply-To: <Pine.LNX.4.64.0703271014100.793@sbz-30.cs.Helsinki.FI>
Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@cs.helsinki.fi>
>
> We need to break COW for private mappings to make sure a process cannot
> read new data after an inode has been revoked.
Seems OK.
>
> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
> ---
> fs/revoke.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 73 insertions(+), 12 deletions(-)
>
> Index: uml-2.6/fs/revoke.c
> ===================================================================
> --- uml-2.6.orig/fs/revoke.c 2007-03-26 18:10:24.000000000 +0300
> +++ uml-2.6/fs/revoke.c 2007-03-26 18:27:25.000000000 +0300
> @@ -174,12 +174,58 @@ static inline bool need_revoke(struct vm
> if (file->f_path.dentry->d_inode != inode)
> return false;
>
> - if (!(vma->vm_flags & VM_SHARED))
> - return false;
> -
> return file != to_exclude;
> }
>
> +static int __revoke_break_cow(struct task_struct *tsk, struct inode *inode,
> + struct file *to_exclude)
> +{
> + struct mm_struct *mm = tsk->mm;
> + struct vm_area_struct *vma;
> + int err = 0;
> +
> + down_write(&mm->mmap_sem);
> + for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
> + int ret;
> +
> + if (vma->vm_flags & VM_SHARED)
> + continue;
> +
> + if (!need_revoke(vma, inode, to_exclude))
> + continue;
> +
> + ret = get_user_pages(tsk, tsk->mm, vma->vm_start,
> + vma->vm_end-vma->vm_start, 1, 1, NULL,
> + NULL);
get_user_pages length argument is in # of pages, rather than address range,
I think. vma_pages is what you want?
> + if (ret < 0) {
> + err = ret;
> + break;
> + }
> + }
> + up_write(&mm->mmap_sem);
I think you just need down_read of mmap_sem here?
--
SUSE Labs, Novell Inc.
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next prev parent reply other threads:[~2007-03-28 8:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-27 7:14 [PATCH 2/2] revoke: break cow for private mappings Pekka J Enberg
2007-03-28 8:04 ` Nick Piggin [this message]
2007-03-28 10:09 ` Pekka Enberg
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