RE: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs

From: David Laight <David.Laight@ACULAB.COM>
To: 'Joe Perches' <joe@perches.com>, Julia Lawall <julia.lawall@inria.fr>
Cc: Alex Dewar <alex.dewar90@gmail.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	cocci <cocci@systeme.lip6.fr>, Kees Cook <keescook@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	"accessrunner-general@lists.sourceforge.net" 
	<accessrunner-general@lists.sourceforge.net>
Subject: RE: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs
Date: Thu, 27 Aug 2020 22:03:20 +0000	[thread overview]
Message-ID: <c3926f18f98e446daad957cd66a94890@AcuMS.aculab.com> (raw)
In-Reply-To: <cf9b1ea3716305447be43bffc8f90b7ef7292f5b.camel@perches.com>

From: Joe Perches
> Sent: 27 August 2020 21:30
...
> Perhaps what's necessary is to find any
> appropriate .show function and change
> any use of strcpy/sprintf within those
> function to some other name.
> 
> For instance:
> 
> drivers/isdn/mISDN/core.c-static ssize_t name_show(struct device *dev,
> drivers/isdn/mISDN/core.c-                       struct device_attribute *attr, char *buf)
> drivers/isdn/mISDN/core.c-{
> drivers/isdn/mISDN/core.c:      strcpy(buf, dev_name(dev));
> drivers/isdn/mISDN/core.c-      return strlen(buf);
> drivers/isdn/mISDN/core.c-}
> drivers/isdn/mISDN/core.c-static DEVICE_ATTR_RO(name);

That form ends up calculating the string length twice.
Better would be:
	len = strlen(msg);
	memcpy(buf, msg, len);
	return len;


	David

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