s390/qeth: fix double-free on IP add/remove race

Registering an IPv4 address with the HW takes quite a while, so we
temporarily drop the ip_htable lock. Any concurrent add/remove of the
same IP adjusts the IP's use count, and (on remove) is then blocked by
addr->in_progress.
After the register call has completed, we check the use count for
concurrently attempted add/remove calls - and possibly straight-away
deregister the IP again. This happens via l3_delete_ip(), which
1) looks up the queried IP in the htable (getting a reference to the
   *same* queried object),
2) deregisters the IP from the HW, and
3) frees the IP object.

The caller in l3_add_ip() then does a second free on the same object.

For this case, skip all the extra checks and lookups in l3_delete_ip()
and just deregister & free the IP object ourselves.

Fixes: 5f78e29ceebf ("qeth: optimize IP handling in rx_mode callback")
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 34481b51029e34cf2e8dde4cab74bdff251f1cc7..77cdb4fc7721eb506165a77ee7b2e6fad277023d 100644 (file)
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -237,7 +237,8 @@ int qeth_l3_add_ip(struct qeth_card *card, struct qeth_ipaddr *tmp_addr)
                                (rc == IPA_RC_LAN_OFFLINE)) {
                        addr->disp_flag = QETH_DISP_ADDR_DO_NOTHING;
                        if (addr->ref_counter < 1) {
-                               qeth_l3_delete_ip(card, addr);
+                               qeth_l3_deregister_addr_entry(card, addr);
+                               hash_del(&addr->hnode);
                                kfree(addr);
                        }
                } else {