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From: David Laight <David.Laight@ACULAB.COM>
To: "'Vivien Didelot'" <vivien.didelot@savoirfairelinux.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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        Sean Wang <sean.wang@mediatek.com>,
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        Chris Healy <cphealy@gmail.com>
Subject: RE: [PATCH net-next v2 02/10] net: dsa: debugfs: add tree
Thread-Topic: [PATCH net-next v2 02/10] net: dsa: debugfs: add tree
Thread-Index: AQHTKLNYd4qu2EQuz0+ayl6nngAvPaKrFYGA
Date: Fri, 8 Sep 2017 15:03:16 +0000
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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