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 <[email protected]> know about it.

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

From: Julian Wiedmann <[email protected]>

[ 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.

---
 drivers/s390/net/qeth_l3_main.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -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 [email protected] 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