[PATCH v4] IB/mlx4: Fix refcount leak in add_port() error path

[Guangshuo Li <lgs201920130244@gmail.com>]

After kobject_init_and_add(), the lifetime of the embedded struct
kobject is expected to be managed through the kobject core reference
counting.

In add_port(), several failure paths after kobject_init_and_add() free
struct mlx4_port directly instead of releasing the embedded kobject with
kobject_put(). This leaves the kobject reference count unbalanced and can
lead to incorrect lifetime handling.

Fix this by routing all failures after kobject_init_and_add() through a
single kobject_put() based error path. Since the release callback may now
be called for partially initialized mlx4_port objects, make
mlx4_port_release() tolerate NULL attribute arrays.

The issue was identified by a static analysis tool I developed and
confirmed by manual review.

Fixes: c1e7e466120b ("IB/mlx4: Add iov directory in sysfs under the ib device")
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
v4:
  - route all add_port() failures after kobject_init_and_add() through
    a single kobject_put() based error path
  - remove duplicated attribute array frees from add_port()
  - keep mlx4_port_release() tolerant of partially initialized objects

v3:
  - make mlx4_port_release() tolerate NULL attribute arrays
  - drop the parent kobject reference on the kobject_init_and_add()
    failure path before putting the embedded kobject

v2:
  - note that the issue was identified by my static analysis tool
  - and confirmed by manual review

 drivers/infiniband/hw/mlx4/sysfs.c | 44 ++++++++++++++----------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/drivers/infiniband/hw/mlx4/sysfs.c b/drivers/infiniband/hw/mlx4/sysfs.c
index b8fa4ecfc961..fe505e07849d 100644
--- a/drivers/infiniband/hw/mlx4/sysfs.c
+++ b/drivers/infiniband/hw/mlx4/sysfs.c
@@ -380,12 +380,17 @@ static void mlx4_port_release(struct kobject *kobj)
 	struct attribute *a;
 	int i;
 
-	for (i = 0; (a = p->pkey_group.attrs[i]); ++i)
-		kfree(a);
-	kfree(p->pkey_group.attrs);
-	for (i = 0; (a = p->gid_group.attrs[i]); ++i)
-		kfree(a);
-	kfree(p->gid_group.attrs);
+	if (p->pkey_group.attrs) {
+		for (i = 0; (a = p->pkey_group.attrs[i]); ++i)
+			kfree(a);
+		kfree(p->pkey_group.attrs);
+	}
+
+	if (p->gid_group.attrs) {
+		for (i = 0; (a = p->gid_group.attrs[i]); ++i)
+			kfree(a);
+		kfree(p->gid_group.attrs);
+	}
 	kfree(p);
 }
 
@@ -623,7 +628,6 @@ static void remove_vf_smi_entries(struct mlx4_port *p)
 static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
 {
 	struct mlx4_port *p;
-	int i;
 	int ret;
 	int is_eth = rdma_port_get_link_layer(&dev->ib_dev, port_num) ==
 			IB_LINK_LAYER_ETHERNET;
@@ -640,7 +644,7 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
 				   kobject_get(dev->dev_ports_parent[slave]),
 				   "%d", port_num);
 	if (ret)
-		goto err_alloc;
+		goto err_put;
 
 	p->pkey_group.name  = "pkey_idx";
 	p->pkey_group.attrs =
@@ -649,44 +653,36 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
 				  dev->dev->caps.pkey_table_len[port_num]);
 	if (!p->pkey_group.attrs) {
 		ret = -ENOMEM;
-		goto err_alloc;
+		goto err_put;
 	}
 
 	ret = sysfs_create_group(&p->kobj, &p->pkey_group);
 	if (ret)
-		goto err_free_pkey;
+		goto err_put;
 
 	p->gid_group.name  = "gid_idx";
 	p->gid_group.attrs = alloc_group_attrs(show_port_gid_idx, NULL, 1);
 	if (!p->gid_group.attrs) {
 		ret = -ENOMEM;
-		goto err_free_pkey;
+		goto err_put;
 	}
 
 	ret = sysfs_create_group(&p->kobj, &p->gid_group);
 	if (ret)
-		goto err_free_gid;
+		goto err_put;
 
 	ret = add_vf_smi_entries(p);
 	if (ret)
-		goto err_free_gid;
+		goto err_put;
 
 	list_add_tail(&p->kobj.entry, &dev->pkeys.pkey_port_list[slave]);
 	return 0;
 
-err_free_gid:
-	kfree(p->gid_group.attrs[0]);
-	kfree(p->gid_group.attrs);
-
-err_free_pkey:
-	for (i = 0; i < dev->dev->caps.pkey_table_len[port_num]; ++i)
-		kfree(p->pkey_group.attrs[i]);
-	kfree(p->pkey_group.attrs);
-
-err_alloc:
+err_put:
 	kobject_put(dev->dev_ports_parent[slave]);
-	kfree(p);
+	kobject_put(&p->kobj);
 	return ret;
+
 }
 
 static int register_one_pkey_tree(struct mlx4_ib_dev *dev, int slave)
-- 
2.43.0