[Intel-wired-lan] [PATCH] i40e: fix NULL pointer dereference in i40e_lan_del_device()

[Linkui Xiao <xiaolinkui@126.com>]

From: Linkui Xiao <xiaolinkui@kylinos.cn>

i40e_lan_del_device() dereferences pf->cinst unconditionally. pf->cinst
is only assigned by i40e_client_add_instance(), which resets it to NULL
whenever the i40e_client_instance allocation, i40e_client_get_params()
or i40e_register_auxiliary_dev() fails, and it returns void so
i40e_lan_add_device() cannot report any of that to its caller.

i40e_lan_add_device() can also fail before it ever gets there, for
example when the i40e_device allocation fails, and i40e_probe() only
prints a message instead of clearing I40E_FLAG_IWARP_ENA. i40e_remove()
therefore still calls i40e_lan_del_device() and dereferences a NULL
pf->cinst.

Only tear the auxiliary device down when an instance was actually
created. Removing the PF from the i40e_devices list below does not
depend on it.

Fixes: f4370a85d62e ("i40e: Register auxiliary devices to provide RDMA")
Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
---
 drivers/net/ethernet/intel/i40e/i40e_client.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_client.c b/drivers/net/ethernet/intel/i40e/i40e_client.c
index 84a97ca8a6d8..9a4f50af5347 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_client.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_client.c
@@ -496,15 +496,22 @@ int i40e_lan_add_device(struct i40e_pf *pf)
  **/
 int i40e_lan_del_device(struct i40e_pf *pf)
 {
-	struct auxiliary_device *aux_dev = pf->cinst->lan_info.aux_dev;
+	struct auxiliary_device *aux_dev;
 	struct i40e_device *ldev, *tmp;
 	int ret = -ENODEV;
 
-	auxiliary_device_delete(aux_dev);
-	auxiliary_device_uninit(aux_dev);
+	/* i40e_client_add_instance() leaves pf->cinst NULL when it fails,
+	 * so there may be no auxiliary device to tear down here.
+	 */
+	if (pf->cinst) {
+		aux_dev = pf->cinst->lan_info.aux_dev;
 
-	/* First, remove any client instance. */
-	i40e_client_del_instance(pf);
+		auxiliary_device_delete(aux_dev);
+		auxiliary_device_uninit(aux_dev);
+
+		/* First, remove any client instance. */
+		i40e_client_del_instance(pf);
+	}
 
 	mutex_lock(&i40e_device_mutex);
 	list_for_each_entry_safe(ldev, tmp, &i40e_devices, list) {
-- 
2.25.1