netdev - Re: [PATCH v2 1/5] hwmon: introduce hwmon_sanitize

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Date:   Wed, 30 Mar 2022 22:51:37 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Michael Walle <michael@...le.cc>, Tom Rix <trix@...hat.com>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] hwmon: introduce hwmon_sanitize_name()

On Wed, Mar 30, 2022 at 10:11:39AM +0000, David Laight wrote:
> From: Xu Yilun
> > Sent: 30 March 2022 07:51
> > 
> > On Tue, Mar 29, 2022 at 06:07:26PM +0200, Michael Walle wrote:
> > > More and more drivers will check for bad characters in the hwmon name
> > > and all are using the same code snippet. Consolidate that code by adding
> > > a new hwmon_sanitize_name() function.
> > >
> > > Signed-off-by: Michael Walle <michael@...le.cc>
> > > ---
> > >  Documentation/hwmon/hwmon-kernel-api.rst |  9 ++++-
> > >  drivers/hwmon/hwmon.c                    | 49 ++++++++++++++++++++++++
> > >  include/linux/hwmon.h                    |  3 ++
> > >  3 files changed, 60 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/hwmon/hwmon-kernel-api.rst b/Documentation/hwmon/hwmon-kernel-api.rst
> > > index c41eb6108103..12f4a9bcef04 100644
> > > --- a/Documentation/hwmon/hwmon-kernel-api.rst
> > > +++ b/Documentation/hwmon/hwmon-kernel-api.rst
> > > @@ -50,6 +50,10 @@ register/unregister functions::
> > >
> > >    void devm_hwmon_device_unregister(struct device *dev);
> > >
> > > +  char *hwmon_sanitize_name(const char *name);
> > > +
> > > +  char *devm_hwmon_sanitize_name(struct device *dev, const char *name);
> > > +
> > >  hwmon_device_register_with_groups registers a hardware monitoring device.
> > >  The first parameter of this function is a pointer to the parent device.
> > >  The name parameter is a pointer to the hwmon device name. The registration
> > > @@ -93,7 +97,10 @@ removal would be too late.
> > >
> > >  All supported hwmon device registration functions only accept valid device
> > >  names. Device names including invalid characters (whitespace, '*', or '-')
> > > -will be rejected. The 'name' parameter is mandatory.
> > > +will be rejected. The 'name' parameter is mandatory. Before calling a
> > > +register function you should either use hwmon_sanitize_name or
> > > +devm_hwmon_sanitize_name to replace any invalid characters with an
> > 
> > I suggest                   to duplicate the name and replace ...
> 
> You are now going to get code that passed in NULL when the kmalloc() fails.
> If 'sanitizing' the name is the correct thing to do then sanitize it
> when the copy is made into the allocated structure.

Then the driver is unaware of the name change, which makes more
confusing.

> (I'm assuming that the 'const char *name' parameter doesn't have to
> be persistent - that would be another bug just waiting to happen.)

The hwmon core does require a persistent "name" parameter now. No name
copy is made when hwmon dev register.

> 
> Seems really pointless to be do a kmalloc() just to pass a string
> into a function.

Maybe we should not force a kmalloc() when the sanitizing is needed, let
the driver decide whether to duplicate the string or not.

Thanks,
Yilun

> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)