linux-kernel - Re: [PATCH v2] thunderbolt: Fix to check return value of ida_simple

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Date:   Thu, 21 Mar 2019 07:49:33 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Mukesh Ojha <mojha@...eaurora.org>
Cc:     Aditya Pakki <pakki001@....edu>, kjlu@....edu,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] thunderbolt: Fix to check return value of
 ida_simple_get

On Thu, Mar 21, 2019 at 02:09:41AM +0530, Mukesh Ojha wrote:
> 
> On 3/20/2019 9:59 PM, Mika Westerberg wrote:
> > On Wed, Mar 20, 2019 at 11:24:45AM -0500, Aditya Pakki wrote:
> > > In enumerate_services, ida_simple_get on failure can return an error and
> > > leaks memory during device_register failure. The patch ensures that
> > > the dev_set_name is set on non failure cases, and releases memory in
> > > case of failure.
> > > 
> > > Signed-off-by: Aditya Pakki <pakki001@....edu>
> > > 
> > > ---
> > > v1: Missed cleanup of svc in case of allocation failure and
> > > device_register failure.
> > > ---
> > >   drivers/thunderbolt/xdomain.c | 9 ++++++++-
> > >   1 file changed, 8 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/thunderbolt/xdomain.c b/drivers/thunderbolt/xdomain.c
> > > index e27dd8beb94b..eb08275185bf 100644
> > > --- a/drivers/thunderbolt/xdomain.c
> > > +++ b/drivers/thunderbolt/xdomain.c
> > > @@ -740,6 +740,7 @@ static void enumerate_services(struct tb_xdomain *xd)
> > >   	struct tb_service *svc;
> > >   	struct tb_property *p;
> > >   	struct device *dev;
> > > +	int id;
> > >   	/*
> > >   	 * First remove all services that are not available anymore in
> > > @@ -768,7 +769,12 @@ static void enumerate_services(struct tb_xdomain *xd)
> > >   			break;
> > >   		}
> > > -		svc->id = ida_simple_get(&xd->service_ids, 0, 0, GFP_KERNEL);
> > > +		id = ida_simple_get(&xd->service_ids, 0, 0, GFP_KERNEL);
> > > +		if (id < 0) {
> > > +			kfree(svc);
> > > +			break;
> > > +		}
> > > +		svc->id = id;
> > >   		svc->dev.bus = &tb_bus_type;
> > >   		svc->dev.type = &tb_service_type;
> > >   		svc->dev.parent = &xd->dev;
> > > @@ -776,6 +782,7 @@ static void enumerate_services(struct tb_xdomain *xd)
> > >   		if (device_register(&svc->dev)) {
> > >   			put_device(&svc->dev);
> > > +			kfree(svc);
> > You can't do this after device_register() is called. The put_device()
> > above is sufficient.
> 
> 
> If  device_register fails, how would svc gets freed? we need  to kfree svc
> here as well.

Please read the comment on top of device_register(). It should explain.

So no kfree here.