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

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Date:   Thu, 27 Aug 2020 22:03:20 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Joe Perches' <joe@...ches.com>,
        Julia Lawall <julia.lawall@...ia.fr>
CC:     Alex Dewar <alex.dewar90@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        cocci <cocci@...teme.lip6.fr>, Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        "accessrunner-general@...ts.sourceforge.net" 
        <accessrunner-general@...ts.sourceforge.net>
Subject: RE: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs

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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