Re: [ovs-dev] [PATCH v2] net: openvswitch: fix possible memory leak in ovs_meter_cmd_set()

[Hangyu Hua]

On 9/2/2023 21:42, Eelco Chaudron wrote:
> On 9 Feb 2023, at 11:58, Simon Horman wrote:
>
> > On Thu, Feb 09, 2023 at 05:32:40PM +0800, Hangyu Hua wrote:
> > > old_meter needs to be free after it is detached regardless of whether
> > > the new meter is successfully attached.
> > >
> > > Fixes: c7c4c44c9a95 ("net: openvswitch: expand the meters supported number")
> > > Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> > > ---
> > >
> > > v2: use goto label and free old_meter outside of ovs lock.
> > >
> > >   net/openvswitch/meter.c | 12 +++++++++---
> > >   1 file changed, 9 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
> > > index 6e38f68f88c2..9b680f0894f1 100644
> > > --- a/net/openvswitch/meter.c
> > > +++ b/net/openvswitch/meter.c
> > > @@ -417,6 +417,7 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
> > >   	int err;
> > >   	u32 meter_id;
> > >   	bool failed;
> > > +	bool locked = true;
> > >
> > >   	if (!a[OVS_METER_ATTR_ID])
> > >   		return -EINVAL;
> > > @@ -448,11 +449,13 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
> > >   		goto exit_unlock;
> > >
> > >   	err = attach_meter(meter_tbl, meter);
> > > -	if (err)
> > > -		goto exit_unlock;
> > >
> > >   	ovs_unlock();
> > >
> > > +	if (err) {
> > > +		locked = false;
> > > +		goto exit_free_old_meter;
> > > +	}
> > >   	/* Build response with the meter_id and stats from
> > >   	 * the old meter, if any.
> > >   	 */
> > > @@ -472,8 +475,11 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
> > >   	genlmsg_end(reply, ovs_reply_header);
> > >   	return genlmsg_reply(reply, info);
> > >
> > > +exit_free_old_meter:
> > > +	ovs_meter_free(old_meter);
> > >   exit_unlock:
> > > -	ovs_unlock();
> > > +	if (locked)
> > > +		ovs_unlock();
> >
> > I see where you are going here, but is the complexity of the
> > locked variable worth the benefit of freeing old_meter outside
> > the lock?
>
> Looking at the error path, I would agree with Simon, and just add an “exit_free_old_meter” label as suggested in v1 and keep the lock in place to make the error path more straightforward.
>
> //Eelco

I see. I will send a v3 later.

Thanks,
Hangyu

> > >   	nlmsg_free(reply);
> > >   exit_free_meter:
> > >   	kfree(meter);
> > > --
> > > 2.34.1
> > >
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