Patch "s390/qeth: Fix potential loss of L3-IP@ in case of network issues" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    s390/qeth: Fix potential loss of L3-IP@ in case of network issues

to the 5.4-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-qeth-fix-potential-loss-of-l3-ip-in-case-of-net.patch
and it can be found in the queue-5.4 subdirectory.

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



commit 1fbc7fc5f8e90792ee1c8500f1b572257d8b5456
Author: Alexandra Winter <wintera@xxxxxxxxxxxxx>
Date:   Tue Feb 6 09:58:49 2024 +0100

    s390/qeth: Fix potential loss of L3-IP@ in case of network issues
    
    [ Upstream commit 2fe8a236436fe40d8d26a1af8d150fc80f04ee1a ]
    
    Symptom:
    In case of a bad cable connection (e.g. dirty optics) a fast sequence of
    network DOWN-UP-DOWN-UP could happen. UP triggers recovery of the qeth
    interface. In case of a second DOWN while recovery is still ongoing, it
    can happen that the IP@ of a Layer3 qeth interface is lost and will not
    be recovered by the second UP.
    
    Problem:
    When registration of IP addresses with Layer 3 qeth devices fails, (e.g.
    because of bad address format) the respective IP address is deleted from
    its hash-table in the driver. If registration fails because of a ENETDOWN
    condition, the address should stay in the hashtable, so a subsequent
    recovery can restore it.
    
    3caa4af834df ("qeth: keep ip-address after LAN_OFFLINE failure")
    fixes this for registration failures during normal operation, but not
    during recovery.
    
    Solution:
    Keep L3-IP address in case of ENETDOWN in qeth_l3_recover_ip(). For
    consistency with qeth_l3_add_ip() we also keep it in case of EADDRINUSE,
    i.e. for some reason the card already/still has this address registered.
    
    Fixes: 4a71df50047f ("qeth: new qeth device driver")
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: Alexandra Winter <wintera@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240206085849.2902775-1-wintera@xxxxxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 8dee16aca421f..fe2bea2409427 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -305,9 +305,10 @@ static void qeth_l3_clear_ip_htable(struct qeth_card *card, int recover)
 		if (!recover) {
 			hash_del(&addr->hnode);
 			kfree(addr);
-			continue;
+		} else {
+			/* prepare for recovery */
+			addr->disp_flag = QETH_DISP_ADDR_ADD;
 		}
-		addr->disp_flag = QETH_DISP_ADDR_ADD;
 	}
 
 	mutex_unlock(&card->ip_lock);
@@ -335,11 +336,13 @@ static void qeth_l3_recover_ip(struct qeth_card *card)
 			} else
 				rc = qeth_l3_register_addr_entry(card, addr);
 
-			if (!rc) {
+			if (!rc || rc == -EADDRINUSE || rc == -ENETDOWN) {
+				/* keep it in the records */
 				addr->disp_flag = QETH_DISP_ADDR_DO_NOTHING;
 				if (addr->ref_counter < 1)
 					qeth_l3_delete_ip(card, addr);
 			} else {
+				/* bad address */
 				hash_del(&addr->hnode);
 				kfree(addr);
 			}