linux-kernel - Re: [PATCH] vfs: fix possible use after free in finish

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Message-ID: <20101029065819.GQ19804@ZenIV.linux.org.uk>
Date:	Fri, 29 Oct 2010 07:58:19 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: fix possible use after free in finish_open()

On Tue, Oct 26, 2010 at 12:28:48PM +0200, Miklos Szeredi wrote:
> Oops, broken patch.  Here's the correct one.
> 
> ----
> Subject: vfs: fix possible use after free in finish_open()
> 
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> In finish_open() nd->path is used after nameidata_to_filp() already
> released it.  Fix by acquiring a ref to nd->path and releasing after
> the last use.

Nice catch, but I'd do it differently; that is, do not drop reference
in nameidata_to_filp() (and dup it if we do __dentry_open()) and drop
it in callers instead.  Will push in a few.
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