linux-kernel - RE: [PATCH v2 1/5] hwmon: introduce hwmon_sanitize

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Date:   Wed, 30 Mar 2022 14:50:02 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Guenter Roeck' <linux@...ck-us.net>,
        Michael Walle <michael@...le.cc>,
        "Xu Yilun" <yilun.xu@...el.com>, Tom Rix <trix@...hat.com>,
        Jean Delvare <jdelvare@...e.com>, 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>
CC:     "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()

From: Guenter Roeck
> Sent: 30 March 2022 15:23
> On 3/29/22 09:07, 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
> > +underscore.
> 
> That needs more details and deserves its own paragraph. Calling one of
> the functions is only necessary if the original name does or can include
> unsupported characters; an unconditional "should" is therefore a bit
> strong. Also, it is important to mention that the function duplicates
> the name, and that it is the responsibility of the caller to release
> the name if hwmon_sanitize_name() was called and the device is removed.

More worrying, and not documented, is that the buffer 'name' points
to must persist.

ISTM that the kmalloc() in __hwmon_device_register() should include
space for a copy of the name.
It can then do what it will with whatever is passed in.

Oh yes, it has my 'favourite construct':  if (!strlen(name)) ...
(well str[strlen(str)] = 0 also happens!)

	David

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