Patch "s390/qeth: fix double-free on IP add/remove race" has been added to the 4.9-stable tree

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

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

to the 4.9-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-double-free-on-ip-add-remove-race.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let [off-list ref] know about it.

From foo@baz Thu Mar  8 06:55:02 PST 2018

From: Julian Wiedmann <redacted>
Date: Tue, 27 Feb 2018 18:58:14 +0100
Subject: s390/qeth: fix double-free on IP add/remove race

From: Julian Wiedmann <redacted>


[ Upstream commit 14d066c3531a87f727968cacd85bd95c75f59843 ]

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 <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/s390/net/qeth_l3_main.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c

@@ -323,7 +323,8 @@ int qeth_l3_add_ip(struct qeth_card *car
 				(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 {

Patches currently in stable-queue which might be from jwi@linux.vnet.ibm.com are

queue-4.9/s390-qeth-fix-setip-command-handling.patch
queue-4.9/s390-qeth-fix-ip-address-lookup-for-l3-devices.patch
queue-4.9/s390-qeth-fix-ipa-command-submission-race.patch
queue-4.9/s390-qeth-fix-overestimated-count-of-buffer-elements.patch
queue-4.9/s390-qeth-fix-double-free-on-ip-add-remove-race.patch
queue-4.9/s390-qeth-fix-ip-removal-on-offline-cards.patch
queue-4.9/s390-qeth-fix-underestimated-count-of-buffer-elements.patch