[Bug 1800639] Re: [Ubuntu] net/af_iucv: fix skb leaks for HiperTransport

** Changed in: linux (Ubuntu)
Status: In Progress => Fix Committed

** Changed in: ubuntu-z-systems
Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/1800639

Title:
[Ubuntu] net/af_iucv: fix skb leaks for HiperTransport

Status in Ubuntu on IBM z Systems:
Fix Committed
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Xenial:
Fix Committed
Status in linux source package in Bionic:
Fix Committed
Status in linux source package in Cosmic:
Fix Committed

Bug description:
== SRU Justification ==

Fix socket buffer (skb) leaks for HiperTransport

Description: net/af_iucv: fix skb leaks for HiperTransport
Symptom: Memory leaks and/or double-freed network packets.
Problem: Inbound packets may have any combination of flag bits set in
their iucv header. Current code only handles certain
combinations, and ignores (ie. leaks) all packets with other flags.

On Transmit, current code is inconsistent about whether the error
paths need to free the skb. Depending on which error path is
taken, it may either get freed twice, or leak.
Solution: On receive, drop any skb with an unexpected combination of iucv
Header flags.
On transmit, be consistent in all error paths about free'ing the skb.

== Fix ==

222440996d6daf635bed6cb35041be22ede3e8a0 ("net/af_iucv: drop inbound packets with invalid flags")
b2f543949acd1ba64313fdad9e672ef47550d773 ("net/af_iucv: fix skb handling on HiperTransport xmit error")

== Patch ==

commit 222440996d6daf635bed6cb35041be22ede3e8a0
Author: Julian Wiedmann <jwi@linux.ibm.com>
Date: Wed Sep 5 16:55:10 2018 +0200

net/af_iucv: drop inbound packets with invalid flags

Inbound packets may have any combination of flag bits set in their iucv
header. If we don't know how to handle a specific combination, drop the
skb instead of leaking it.

To clarify what error is returned in this case, replace the hard-coded
0 with the corresponding macro.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

==

commit b2f543949acd1ba64313fdad9e672ef47550d773
Author: Julian Wiedmann <jwi@linux.ibm.com>
Date: Wed Sep 5 16:55:11 2018 +0200

net/af_iucv: fix skb handling on HiperTransport xmit error

When sending an skb, afiucv_hs_send() bails out on various error
conditions. But currently the caller has no way of telling whether the
skb was freed or not - resulting in potentially either
a) leaked skbs from iucv_send_ctrl(), or
b) double-free's from iucv_sock_sendmsg().

As dev_queue_xmit() will always consume the skb (even on error), be
consistent and also free the skb from all other error paths. This way
callers no longer need to care about managing the skb.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

== Regression Potential ==

Low, because:

- IUCV functionality is very special to s390x and is only supported in z/VM environments
(z/VM hypervisor to guest or guest to guest communications)
- So everything is s390x specific.
- Patch is limited to this single file: /net/iucv/af_iucv.c
- Patch was tested by IBM, and fixes an identified problem situation.

== Test Case ==

Set IUCV communication on an Ubuntu s390x system that runs as z/VM guest:
https://www.ibm.com/support/knowledgecenter/en/linuxonibm/com.ibm.linux.z.ludd/ludd_r_afiucv_setup.html
Provoke an error situation.
This is btw. hard to do, because the 'Inter-User Communication Vehicle" (IUCV) is a virtual z/VM internal
network that does not use any real media.
To check for regressions one can use a shell over an ssh connection using an IUCV interface
or use an application that utilises AF_IUCV sockets (like ICC).
__________

Description: net/af_iucv: fix skb leaks for HiperTransport
Symptom: Memory leaks and/or double-freed network packets.
Problem: Inbound packets may have any combination of flag bits set in
their iucv header. Current code only handles certain
combinations, and ignores (ie. leaks) all packets with other
flags.

On Transmit, current code is inconsistent about whether the error
paths need to free the skb. Depending on which error path is
taken, it may either get freed twice, or leak.
Solution: On receive, drop any skb with an unexpected combination of iucv
Header flags.
On transmit, be consistent in all error paths about free'ing the
skb.

kerne 4.19
Upstream-ID: 222440996d6daf635bed6cb35041be22ede3e8a0
b2f543949acd1ba64313fdad9e672ef47550d773

Should also be applied, to all other Ubuntu Releases in the field !

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