linux-kernel - Re: [PATCH v3 1/2] pci: endpoint: Simplify name allocation for epf device

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Date:   Tue, 27 Feb 2018 11:15:58 +0100 (CET)
From:   Rolf Evers-Fischer <embedded24@...rs-fischer.de>
To:     Kishon Vijay Abraham I <kishon@...com>
cc:     Rolf Evers-Fischer <embedded24@...rs-fischer.de>,
        lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        andy.shevchenko@...il.com,
        Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>
Subject: Re: [PATCH v3 1/2] pci: endpoint: Simplify name allocation for epf
 device

Hi,

On Tue, 27 Feb 2018, Kishon Vijay Abraham I wrote:

> Hi,
> 
> On Tuesday 27 February 2018 03:32 PM, Rolf Evers-Fischer wrote:
> > From: Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>
> > 
> > This commit replaces allocating and freeing the intermediate
> > 'buf'/'func_name' with a combination of 'kstrndup()' and 'len'.
> > 
> > 'len' is the required length of 'epf->name'.
> > 'epf->name' should be either the first part of 'name' preceding the '.'
> > or the complete 'name', if there is no '.' in the name.
> > 
> > Signed-off-by: Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>
> > ---
> >  drivers/pci/endpoint/pci-epf-core.c | 22 ++++------------------
> >  1 file changed, 4 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> > index 766ce1dca2ec..1f2506f32bb9 100644
> > --- a/drivers/pci/endpoint/pci-epf-core.c
> > +++ b/drivers/pci/endpoint/pci-epf-core.c
> > @@ -200,8 +200,7 @@ struct pci_epf *pci_epf_create(const char *name)
> >  	int ret;
> >  	struct pci_epf *epf;
> >  	struct device *dev;
> > -	char *func_name;
> > -	char *buf;
> > +	int len;
> >  
> >  	epf = kzalloc(sizeof(*epf), GFP_KERNEL);
> >  	if (!epf) {
> > @@ -209,20 +208,11 @@ struct pci_epf *pci_epf_create(const char *name)
> >  		goto err_ret;
> >  	}
> >  
> > -	buf = kstrdup(name, GFP_KERNEL);
> > -	if (!buf) {
> > -		ret = -ENOMEM;
> > -		goto free_epf;
> > -	}
> > -
> > -	func_name = buf;
> > -	buf = strchrnul(buf, '.');
> > -	*buf = '\0';
> > -
> > -	epf->name = kstrdup(func_name, GFP_KERNEL);
> > +	len = strchrnul(name, '.') - name;
> > +	epf->name = kstrndup(name, len, GFP_KERNEL);
> 
> shouldn't the string end with '\0'?
> 

I agree, it should end with '\0', but fortunately the 'kstrndup()' 
function already adds it for us, see mm/util.c, line 100:
	(...)
	memcpy(buf, s, len);
	buf[len] = '\0';
	(...)

Kind regards
 Rolf