Patch "s390/ism: Do not unregister clients with registered DMBs" has been added to the 6.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    s390/ism: Do not unregister clients with registered DMBs

to the 6.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-ism-do-not-unregister-clients-with-registered-d.patch
and it can be found in the queue-6.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8c9160ca105b8a4c5e9cc7c58c474696aba788c3
Author: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
Date:   Fri Jul 7 12:56:22 2023 +0200

    s390/ism: Do not unregister clients with registered DMBs
    
    [ Upstream commit 266deeea34ffd28c6b6a63edf2af9b5a07161c24 ]
    
    When ism_unregister_client() is called but the client still has DMBs
    registered it returns -EBUSY and prints an error. This only happens
    after the client has already been unregistered however. This is
    unexpected as the unregister claims to have failed. Furthermore as this
    implies a client bug a WARN() is more appropriate. Thus move the
    deregistration after the check and use WARN().
    
    Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration")
    Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index d65571b3d5cad..6db5cf7e901f9 100644
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -96,29 +96,32 @@ int ism_unregister_client(struct ism_client *client)
 	int rc = 0;
 
 	mutex_lock(&ism_dev_list.mutex);
-	mutex_lock(&clients_lock);
-	clients[client->id] = NULL;
-	if (client->id + 1 == max_client)
-		max_client--;
-	mutex_unlock(&clients_lock);
 	list_for_each_entry(ism, &ism_dev_list.list, list) {
 		spin_lock_irqsave(&ism->lock, flags);
 		/* Stop forwarding IRQs and events */
 		ism->subs[client->id] = NULL;
 		for (int i = 0; i < ISM_NR_DMBS; ++i) {
 			if (ism->sba_client_arr[i] == client->id) {
-				pr_err("%s: attempt to unregister client '%s'"
-				       "with registered dmb(s)\n", __func__,
-				       client->name);
+				WARN(1, "%s: attempt to unregister '%s' with registered dmb(s)\n",
+				     __func__, client->name);
 				rc = -EBUSY;
-				goto out;
+				goto err_reg_dmb;
 			}
 		}
 		spin_unlock_irqrestore(&ism->lock, flags);
 	}
-out:
 	mutex_unlock(&ism_dev_list.mutex);
 
+	mutex_lock(&clients_lock);
+	clients[client->id] = NULL;
+	if (client->id + 1 == max_client)
+		max_client--;
+	mutex_unlock(&clients_lock);
+	return rc;
+
+err_reg_dmb:
+	spin_unlock_irqrestore(&ism->lock, flags);
+	mutex_unlock(&ism_dev_list.mutex);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(ism_unregister_client);