linux-kernel - RE: [PATCH net-next v2 02/10] net: dsa: debugfs: add tree

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Date:   Fri, 8 Sep 2017 15:03:16 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Vivien Didelot' <vivien.didelot@...oirfairelinux.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...oirfairelinux.com" <kernel@...oirfairelinux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Egil Hjelmeland <privat@...l-hjelmeland.no>,
        John Crispin <john@...ozen.org>,
        Woojung Huh <Woojung.Huh@...rochip.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Chris Healy <cphealy@...il.com>
Subject: RE: [PATCH net-next v2 02/10] net: dsa: debugfs: add tree

From: Vivien Didelot
> Sent: 08 September 2017 15:57
...
> > > Also more important, you will notice what seems to be a bug to me:
> > > I can read or write a file even if I didn't mask the corresponding mode
> > > hence the double check in dsa_debugfs_show and dsa_debugfs_write.
> >
> > The mode can be changed by userspace, you shouldn't ever need to check
> > it in any debugfs calls, right?
> 
> Correct. But this happens even if the file mode isn't changed by
> userspace in the meantime, which seemed weird to me. e.g. echo
> redirected to a -r--r--r-- debugfs entry will call dsa_debugfs_write.

root will be able to write using 'root' permissions, regardless of
the directory entry.

	David