Date: Tue, 22 Feb 2011 12:33:45 -0800
From: Kees Cook <kees.cook@canonical.com>
To: Dan Carpenter <error27@gmail.com>, Greg KH <gregkh@suse.de>,
        linux-kernel@vger.kernel.org, Eugene Teo <eugeneteo@kernel.sg>,
        Ralph Campbell <infinipath@qlogic.com>,
        Roland Dreier <roland@kernel.org>, Sean Hefty <sean.hefty@intel.com>,
        Hal Rosenstock <hal.rosenstock@gmail.com>,
        Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Miklos Szeredi <miklos@szeredi.hu>,
        "J. Bruce Fields" <bfields@fieldses.org>, Neil Brown <neilb@suse.de>,
        Matthew Wilcox <matthew@wil.cx>, James Morris <jmorris@namei.org>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Eric Paris <eparis@parisplace.org>, Nick Piggin <npiggin@kernel.dk>,
        Arnd Bergmann <arnd@arndb.de>, Ian Campbell <ian.campbell@citrix.com>,
        Jarkko Sakkinen <ext-jarkko.2.sakkinen@nokia.com>,
        Tejun Heo <tj@kernel.org>, Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH 2/2] debugfs: only allow root access to debugging
 interfaces
Message-ID: <20110222203345.GG4000@outflux.net>
References: <1298398198-18482-1-git-send-email-kees.cook@canonical.com>
 <1298398198-18482-2-git-send-email-kees.cook@canonical.com>
 <20110222181613.GU4000@outflux.net>
 <20110222191333.GA9991@suse.de>
 <20110222192248.GX4000@outflux.net>
 <20110222193314.GA11033@suse.de>
 <20110222202915.GC1966@bicker>
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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@canonical.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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