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Date: Thu, 10 Dec 2015 04:14:24 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        yalin wang <yalin.wang2010@gmail.com>, Willy Tarreau <w@1wt.eu>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] fs: clear file privilege bits when mmap writing
Message-ID: <20151210041424.GD20997@ZenIV.linux.org.uk>
References: <20151209225148.GA14794@www.outflux.net>
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On Wed, Dec 09, 2015 at 02:51:48PM -0800, Kees Cook wrote:
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3aa514254161..409bd7047e7e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -872,6 +872,7 @@ struct file {
>  	struct list_head	f_tfile_llink;
>  #endif /* #ifdef CONFIG_EPOLL */
>  	struct address_space	*f_mapping;
> +	bool			f_remove_privs;

NAK.  If anything, such things belong in ->f_flags.  _If_ this is worth
doing at all, that is.