[3.13.y-ckt stable] Patch "openvswitch: Zero flows on allocation." has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    openvswitch: Zero flows on allocation.

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt29.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 670207f022bff5e58c4d5cadf7aaf2cbceb6c19b Mon Sep 17 00:00:00 2001
From: Jesse Gross <jesse at nicira.com>
Date: Mon, 21 Sep 2015 20:21:20 -0700
Subject: openvswitch: Zero flows on allocation.

[ Upstream commit ae5f2fb1d51fa128a460bcfbe3c56d7ab8bf6a43 ]

When support for megaflows was introduced, OVS needed to start
installing flows with a mask applied to them. Since masking is an
expensive operation, OVS also had an optimization that would only
take the parts of the flow keys that were covered by a non-zero
mask. The values stored in the remaining pieces should not matter
because they are masked out.

While this works fine for the purposes of matching (which must always
look at the mask), serialization to netlink can be problematic. Since
the flow and the mask are serialized separately, the uninitialized
portions of the flow can be encoded with whatever values happen to be
present.

In terms of functionality, this has little effect since these fields
will be masked out by definition. However, it leaks kernel memory to
userspace, which is a potential security vulnerability. It is also
possible that other code paths could look at the masked key and get
uninitialized data, although this does not currently appear to be an
issue in practice.

This removes the mask optimization for flows that are being installed.
This was always intended to be the case as the mask optimizations were
really targetting per-packet flow operations.

Fixes: 03f0d916 ("openvswitch: Mega flow implementation")
Signed-off-by: Jesse Gross <jesse at nicira.com>
Acked-by: Pravin B Shelar <pshelar at nicira.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/openvswitch/datapath.c   |  2 +-
 net/openvswitch/flow_table.c | 21 ++++++++++++---------
 net/openvswitch/flow_table.h |  2 +-
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index d26706f..f85000b 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -789,7 +789,7 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
 		if (IS_ERR(acts))
 			goto error;

-		ovs_flow_mask_key(&masked_key, &key, &mask);
+		ovs_flow_mask_key(&masked_key, &key, true, &mask);
 		error = ovs_nla_copy_actions(a[OVS_FLOW_ATTR_ACTIONS],
 					     &masked_key, 0, &acts);
 		if (error) {
diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index dd83154..20063bd 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -57,18 +57,21 @@ static u16 range_n_bytes(const struct sw_flow_key_range *range)
 }

 void ovs_flow_mask_key(struct sw_flow_key *dst, const struct sw_flow_key *src,
-		       const struct sw_flow_mask *mask)
+		       bool full, const struct sw_flow_mask *mask)
 {
-	const long *m = (long *)((u8 *)&mask->key + mask->range.start);
-	const long *s = (long *)((u8 *)src + mask->range.start);
-	long *d = (long *)((u8 *)dst + mask->range.start);
+	int start = full ? 0 : mask->range.start;
+	int len = full ? sizeof *dst : range_n_bytes(&mask->range);
+	const long *m = (const long *)((const u8 *)&mask->key + start);
+	const long *s = (const long *)((const u8 *)src + start);
+	long *d = (long *)((u8 *)dst + start);
 	int i;

-	/* The memory outside of the 'mask->range' are not set since
-	 * further operations on 'dst' only uses contents within
-	 * 'mask->range'.
+	/* If 'full' is true then all of 'dst' is fully initialized. Otherwise,
+	 * if 'full' is false the memory outside of the 'mask->range' is left
+	 * uninitialized. This can be used as an optimization when further
+	 * operations on 'dst' only use contents within 'mask->range'.
 	 */
-	for (i = 0; i < range_n_bytes(&mask->range); i += sizeof(long))
+	for (i = 0; i < len; i += sizeof(long))
 		*d++ = *s++ & *m++;
 }

@@ -417,7 +420,7 @@ static struct sw_flow *masked_flow_lookup(struct table_instance *ti,
 	u32 hash;
 	struct sw_flow_key masked_key;

-	ovs_flow_mask_key(&masked_key, unmasked, mask);
+	ovs_flow_mask_key(&masked_key, unmasked, false, mask);
 	hash = flow_hash(&masked_key, key_start, key_end);
 	head = find_bucket(ti, hash);
 	hlist_for_each_entry_rcu(flow, head, hash_node[ti->node_ver]) {
diff --git a/net/openvswitch/flow_table.h b/net/openvswitch/flow_table.h
index 59c15f7..86d07ff 100644
--- a/net/openvswitch/flow_table.h
+++ b/net/openvswitch/flow_table.h
@@ -78,5 +78,5 @@ bool ovs_flow_cmp_unmasked_key(const struct sw_flow *flow,
 			       struct sw_flow_match *match);

 void ovs_flow_mask_key(struct sw_flow_key *dst, const struct sw_flow_key *src,
-		       const struct sw_flow_mask *mask);
+		       bool full, const struct sw_flow_mask *mask);
 #endif /* flow_table.h */
--
1.9.1