linux-kernel - Re: [PATCH 2/2] debugfs: only allow root access to debugging interfaces

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Message-ID: <20110222203345.GG4000@outflux.net>
Date:	Tue, 22 Feb 2011 12:33:45 -0800
From:	Kees Cook <kees.cook@...onical.com>
To:	Dan Carpenter <error27@...il.com>, Greg KH <gregkh@...e.de>,
	linux-kernel@...r.kernel.org, Eugene Teo <eugeneteo@...nel.sg>,
	Ralph Campbell <infinipath@...gic.com>,
	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Miklos Szeredi <miklos@...redi.hu>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Neil Brown <neilb@...e.de>, Matthew Wilcox <matthew@....cx>,
	James Morris <jmorris@...ei.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Eric Paris <eparis@...isplace.org>,
	Nick Piggin <npiggin@...nel.dk>, Arnd Bergmann <arnd@...db.de>,
	Ian Campbell <ian.campbell@...rix.com>,
	Jarkko Sakkinen <ext-jarkko.2.sakkinen@...ia.com>,
	Tejun Heo <tj@...nel.org>,
	Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH 2/2] debugfs: only allow root access to debugging
 interfaces

On Tue, Feb 22, 2011 at 11:29:15PM +0300, Dan Carpenter wrote:
> On Tue, Feb 22, 2011 at 11:33:14AM -0800, Greg KH wrote:
> > Again, let's fix the real problems here, world-writable debugfs files.
> 
> We could just ban them?

That would be nice. This would be much better than relying on
check_patch.pl. Perhaps do this for /sys and /proc/sys too?

Acked-by: Kees Cook <kees.cook@...onical.com>

> 
> diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
> index e7a7a2f..03ae095 100644
> --- a/fs/debugfs/inode.c
> +++ b/fs/debugfs/inode.c
> @@ -223,6 +223,9 @@ struct dentry *debugfs_create_file(const char *name, mode_t mode,
>  
>  	pr_debug("debugfs: creating file '%s'\n",name);
>  
> +	/* don't allow world writable files */
> +	mode &= ~S_IWOTH;
> +
>  	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
>  			      &debugfs_mount_count);
>  	if (error)
-- 
Kees Cook
Ubuntu Security Team
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