linux-kernel - Re: [PATCH net-next v5 1/2] netconsole: Create a allocation helper

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Date:   Fri, 11 Aug 2023 01:58:25 -0700
From:   Breno Leitao <leitao@...ian.org>
To:     Simon Horman <horms@...nel.org>
Cc:     rdunlap@...radead.org, benjamin.poirier@...il.com,
        davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v5 1/2] netconsole: Create a allocation helper

Hello Simon,

On Thu, Aug 10, 2023 at 10:17:18PM +0200, Simon Horman wrote:
> On Thu, Aug 10, 2023 at 02:54:50AM -0700, Breno Leitao wrote:
> > De-duplicate the initialization and allocation code for struct
> > netconsole_target.
> > 
> > The same allocation and initialization code is duplicated in two
> > different places in the netconsole subsystem, when the netconsole target
> > is initialized by command line parameters (alloc_param_target()), and
> > dynamically by sysfs (make_netconsole_target()).
> > 
> > Create a helper function, and call it from the two different functions.
> > 
> > Suggested-by: Eric Dumazet <edumazet@...gle.com>
> > Signed-off-by: Breno Leitao <leitao@...ian.org>
> > ---
> >  drivers/net/netconsole.c | 42 +++++++++++++++++++++-------------------
> >  1 file changed, 22 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> > index 87f18aedd3bd..f93b98d64a3c 100644
> > --- a/drivers/net/netconsole.c
> > +++ b/drivers/net/netconsole.c
> > @@ -167,19 +167,16 @@ static void netconsole_target_put(struct netconsole_target *nt)
> >  
> >  #endif	/* CONFIG_NETCONSOLE_DYNAMIC */
> >  
> > -/* Allocate new target (from boot/module param) and setup netpoll for it */
> > -static struct netconsole_target *alloc_param_target(char *target_config)
> > +/* Allocate and initialize with defaults.
> > + * Note that these targets get their config_item fields zeroed-out.
> > + */
> > +static struct netconsole_target *alloc_and_init(void)
> >  {
> > -	int err = -ENOMEM;
> >  	struct netconsole_target *nt;
> >  
> > -	/*
> > -	 * Allocate and initialize with defaults.
> > -	 * Note that these targets get their config_item fields zeroed-out.
> > -	 */
> >  	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
> >  	if (!nt)
> > -		goto fail;
> > +		return nt;
> >  
> >  	nt->np.name = "netconsole";
> >  	strscpy(nt->np.dev_name, "eth0", IFNAMSIZ);
> > @@ -187,6 +184,21 @@ static struct netconsole_target *alloc_param_target(char *target_config)
> >  	nt->np.remote_port = 6666;
> >  	eth_broadcast_addr(nt->np.remote_mac);
> >  
> > +	return nt;
> > +}
> > +
> > +/* Allocate new target (from boot/module param) and setup netpoll for it */
> > +static struct netconsole_target *alloc_param_target(char *target_config)
> > +{
> > +	struct netconsole_target *nt;
> > +	int err;
> 
> Hi Breno,
> 
> This function returns err.
> However, clang-16 W=1 and Smatch warn that there is a case
> where this may occur without err having being initialised.

That can really happen, if we get into this function:

        if (*target_config == 'r') {
                if (!nt->extended) {
                        pr_err("Netconsole configuration error. Release feature requires extended log message");
                        goto fail;

	fail:
		return ERR_PTR(err);


Let me update it.