[PATCH 5.4 32/84] s390/qeth: Fix potential loss of L3-IP@ in case of network issues

Greg Kroah-Hartman
2024-02-27T14:22:57Z

From: Alexandra Winter <wintera@linux.ibm.com>

[ 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@vger.kernel.org
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Link: https://lore.kernel.org/r/20240206085849.2902775-1-wintera@linux.ibm.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/s390/net/qeth_l3_main.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

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);
}
--
2.43.0