linux-kernel - Re: [PATCH 2/3] sysfs: Only accept read/write permissions for file attributes

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Message-ID: <20150120171312.GA24203@roeck-us.net>
Date:	Tue, 20 Jan 2015 09:13:12 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, kernel <kernel@...oirfairelinux.com>
Subject: Re: [PATCH 2/3] sysfs: Only accept read/write permissions for file
 attributes

On Tue, Jan 20, 2015 at 10:44:01AM -0500, Vivien Didelot wrote:
> Hi Guenter,
> 
[ ... ]
> 
> > Anyway, my goal was to keep things simple. Taking some bits from the default
> > and others from the return value of the is_visible function isn't simple,
> > even more so since your code would require the is_visible function to mask
> > out SYSFS_PREALLOC to avoid the warning.
> 
> While I'm still not sure about the consequences of flipping this SYSFS_PREALLOC
> bit at runtime, I do agree with your goal.
> 
> Then to keep it simple, the scope of is_visible could be limited to any bit
> allowed at attribute declaration (using *_ATTR* macros). The compile-time check
> macro VERIFY_OCTAL_PERMISSIONS() allows any bit but S_IWOTH. The scope can be
> SYSFS_PREALLOC | 0775. (or 0664 if we want to avoid executables as well.)
> 
> [ This will prevent some follow-up patches "avoid world-writable sysfs files".
> In the future, we may want a runtime equivalent of VERIFY_OCTAL_PERMISSIONS. ]
> 
0775 and 0664 are both fine with me, with a preference for 0664. Before I
resubmit - Greg, any preference from your side ?

Thanks,
Guenter
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