[PATCH net] net/dibs: Correct freeing of dmb_clientid_arr

[PATCH net] net/dibs: Correct freeing of dmb_clientid_arr

[Alexandra Winter]

A dibs device interrupt handler can be active after dibs_dev_del() and
may still access dmb_clientid_arr. (UAF)

In case of a failure in dibs_dev_add() being called by dibs_lo_dev_probe()
dmb_clientid_arr is freed twice (double free).

Free dmb_clientid_arr in dibs_dev_release() after last reference is gone.
Note that allocating in dibs_dev_add() instead of dibs_dev_alloc() is ok
for now, because no dmbs can be registered before dibs_dev_add().

Fixes: cc21191b584c ("dibs: Move data path to dibs layer")
Cc: stable@vger.kernel.org
Co-developed-by: Hidayath Khan <hidayath@linux.ibm.com>
Signed-off-by: Hidayath Khan <hidayath@linux.ibm.com>
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
---
This is a squash of [1] and [2] as requested by Jakub.

Simon and Dust Li, I'd appreciate, if you could double-check whether
you can give R-b again.

Link: https://lore.kernel.org/netdev/20260806120447.596164-1-hidayath@linux.ibm.com/ [1]
Link: https://lore.kernel.org/netdev/20260804085848.3579518-1-wintera@linux.ibm.com/ [2]

 
---
 drivers/dibs/dibs_loopback.c |  1 -
 drivers/dibs/dibs_main.c     | 14 ++++----------
 2 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/dibs/dibs_loopback.c b/drivers/dibs/dibs_loopback.c
index fd5caf1e19a8..649e4e375be3 100644
--- a/drivers/dibs/dibs_loopback.c
+++ b/drivers/dibs/dibs_loopback.c
@@ -335,7 +335,6 @@ static int dibs_lo_dev_probe(void)
 	return 0;
 
 err_reg:
-	kfree(dibs->dmb_clientid_arr);
 	/* pairs with dibs_dev_alloc() */
 	put_device(&dibs->dev);
 	kfree(ldev);
diff --git a/drivers/dibs/dibs_main.c b/drivers/dibs/dibs_main.c
index 4c26fd06973f..2b53a9d277dc 100644
--- a/drivers/dibs/dibs_main.c
+++ b/drivers/dibs/dibs_main.c
@@ -128,6 +128,7 @@ static void dibs_dev_release(struct device *dev)
 
 	dibs = container_of(dev, struct dibs_dev, dev);
 
+	kfree(dibs->dmb_clientid_arr);
 	kfree(dibs);
 }
 
@@ -194,12 +195,13 @@ int dibs_dev_add(struct dibs_dev *dibs)
 
 	ret = device_add(&dibs->dev);
 	if (ret)
-		goto free_client_arr;
+		return ret;
 
 	ret = sysfs_create_group(&dibs->dev.kobj, &dibs_dev_attr_group);
 	if (ret) {
 		dev_err(&dibs->dev, "sysfs_create_group failed for dibs_dev\n");
-		goto err_device_del;
+		device_del(&dibs->dev);
+		return ret;
 	}
 	mutex_lock(&dibs_dev_list.mutex);
 	mutex_lock(&clients_lock);
@@ -214,13 +216,6 @@ int dibs_dev_add(struct dibs_dev *dibs)
 	mutex_unlock(&dibs_dev_list.mutex);
 
 	return 0;
-
-err_device_del:
-	device_del(&dibs->dev);
-free_client_arr:
-	kfree(dibs->dmb_clientid_arr);
-	return ret;
-
 }
 EXPORT_SYMBOL_GPL(dibs_dev_add);
 
@@ -247,7 +242,6 @@ void dibs_dev_del(struct dibs_dev *dibs)
 	mutex_unlock(&dibs_dev_list.mutex);
 
 	device_del(&dibs->dev);
-	kfree(dibs->dmb_clientid_arr);
 }
 EXPORT_SYMBOL_GPL(dibs_dev_del);
 
-- 
2.39.5 (Apple Git-154)