linux-kernel - Re: [PATCH] IB/usnic: Fix memory leak in usnic_ib_sysfs_qpn

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Date:   Wed, 26 Jan 2022 11:47:15 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Christian Benvenuti <benve@...co.com>,
        Nelson Escobar <neescoba@...co.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Upinder Malhi <umalhi@...co.com>,
        Roland Dreier <roland@...estorage.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IB/usnic: Fix memory leak in usnic_ib_sysfs_qpn_add

On Wed, Jan 26, 2022 at 06:04:25AM +0000, Miaoqian Lin wrote:
> kobject_init_and_add() takes reference even when it fails.
> According to the doc of kobject_init_and_add()：
> 
>    If this function returns an error, kobject_put() must be called to
>    properly clean up the memory associated with the object.
> 
> Fix memory leak by calling kobject_put().

There is no real memory leak here, this kobject will be released in
usnic_ib_sysfs_qpn_remove(). Another possible solution is to delete
"if (err)" completely.

diff --git a/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c b/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
index fdb63a8fb997..11723f54e200 100644
--- a/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
+++ b/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
@@ -271,17 +271,15 @@ void usnic_ib_sysfs_unregister_usdev(struct usnic_ib_dev *us_ibdev)
 void usnic_ib_sysfs_qpn_add(struct usnic_ib_qp_grp *qp_grp)
 {
        struct usnic_ib_dev *us_ibdev;
-       int err;
 
        us_ibdev = qp_grp->vf->pf;
 
-       err = kobject_init_and_add(&qp_grp->kobj, &usnic_ib_qpn_type,
+       kobject_init_and_add(&qp_grp->kobj, &usnic_ib_qpn_type,
                        kobject_get(us_ibdev->qpn_kobj),
                        "%d", qp_grp->grp_id);
-       if (err) {
-               kobject_put(us_ibdev->qpn_kobj);
-               return;
-       }
+       /* We don't care about failure here, the release will be performed in
+        * usnic_ib_sysfs_qpn_remove() anyway.
+        */
 }
 
 void usnic_ib_sysfs_qpn_remove(struct usnic_ib_qp_grp *qp_grp)


> 
> Fixes: e3cf00d0a87f ("IB/usnic: Add Cisco VIC low-level hardware driver")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  drivers/infiniband/hw/usnic/usnic_ib_sysfs.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c b/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
> index 7d868f033bbf..69c5854deebc 100644
> --- a/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
> +++ b/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
> @@ -280,6 +280,7 @@ void usnic_ib_sysfs_qpn_add(struct usnic_ib_qp_grp *qp_grp)
>  			kobject_get(us_ibdev->qpn_kobj),
>  			"%d", qp_grp->grp_id);
>  	if (err) {
> +		kobject_put(&qp_grp->kobj);
>  		kobject_put(us_ibdev->qpn_kobj);
>  		return;
>  	}
> -- 
> 2.17.1
>