linux-kernel - Re: [PATCH] fix vulnerability of the release method of file operations in Block layer SCSI generic driver

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Date:	Wed, 10 Nov 2010 08:18:24 -0700
From:	Matthew Wilcox <matthew@....cx>
To:	Hillf Danton <dhillf@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	"Zou, Yi" <yi.zou@...el.com>, Joe Eykholt <jeykholt@...co.com>
Subject: Re: [PATCH] fix vulnerability of the release method of file
	operations in Block layer SCSI generic driver

On Wed, Nov 10, 2010 at 10:08:37PM +0800, Hillf Danton wrote:
> The computation context setup by previous opening the bsg file could
> not survive following open/release operations upon the same file
> object.

Umm .. release is called on final close of a file, not on every close
of a file.

> The vulnerability is fixed by deferring the cleanup operation until necessary.
> 
> Signed-off-by: Hillf Danton <dhillf@...il.com>
> ---
> 
> --- a/block/bsg.c	2010-09-13 07:07:38.000000000 +0800
> +++ b/block/bsg.c	2010-11-10 21:43:58.000000000 +0800
> @@ -858,7 +858,8 @@ static int bsg_release(struct inode *ino
>  {
>  	struct bsg_device *bd = file->private_data;
> 
> -	file->private_data = NULL;
> +	if (1 == atomic_read(&bd->ref_count))
> +		file->private_data = NULL;
>  	return bsg_put_device(bd);
>  }
> --
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-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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