4.2.8-ckt11 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Craig Gallek <kraig@xxxxxxxxxx>
[ Upstream commit d894ba18d4e449b3a7f6eb491f16c9e02933736e ]
With the SO_REUSEPORT socket option, it is possible to create sockets
in the AF_INET and AF_INET6 domains which are bound to the same IPv4 address.
This is only possible with SO_REUSEPORT and when not using IPV6_V6ONLY on
the AF_INET6 sockets.
Prior to the commits referenced below, an incoming IPv4 packet would
always be routed to a socket of type AF_INET when this mixed-mode was used.
After those changes, the same packet would be routed to the most recently
bound socket (if this happened to be an AF_INET6 socket, it would
have an IPv4 mapped IPv6 address).
The change in behavior occurred because the recent SO_REUSEPORT optimizations
short-circuit the socket scoring logic as soon as they find a match. They
did not take into account the scoring logic that favors AF_INET sockets
over AF_INET6 sockets in the event of a tie.
To fix this problem, this patch changes the insertion order of AF_INET
and AF_INET6 addresses in the TCP and UDP socket lists when the sockets
have SO_REUSEPORT set. AF_INET sockets will be inserted at the head of the
list and AF_INET6 sockets with SO_REUSEPORT set will always be inserted at
the tail of the list. This will force AF_INET sockets to always be
considered first.
Fixes: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection")
Fixes: 125e80b88687 ("soreuseport: fast reuseport TCP socket selection")
Reported-by: Maciej Żenczykowski <maze@xxxxxxxxxx>
Signed-off-by: Craig Gallek <kraig@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
include/linux/rculist_nulls.h | 39 +++++++++++++++++++++++++++++++++++++++
include/net/sock.h | 6 +++++-
net/ipv4/udp.c | 9 +++++++--
3 files changed, 51 insertions(+), 3 deletions(-)
diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h
index 1c33dd7..4ae95f7 100644
--- a/include/linux/rculist_nulls.h
+++ b/include/linux/rculist_nulls.h
@@ -98,6 +98,45 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
if (!is_a_nulls(first))
first->pprev = &n->next;
}
+
+/**
+ * hlist_nulls_add_tail_rcu
+ * @n: the element to add to the hash list.
+ * @h: the list to add to.
+ *
+ * Description:
+ * Adds the specified element to the end of the specified hlist_nulls,
+ * while permitting racing traversals. NOTE: tail insertion requires
+ * list traversal.
+ *
+ * The caller must take whatever precautions are necessary
+ * (such as holding appropriate locks) to avoid racing
+ * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
+ * or hlist_nulls_del_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with
+ * the _rcu list-traversal primitives, such as
+ * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency
+ * problems on Alpha CPUs. Regardless of the type of CPU, the
+ * list-traversal primitive must be guarded by rcu_read_lock().
+ */
+static inline void hlist_nulls_add_tail_rcu(struct hlist_nulls_node *n,
+ struct hlist_nulls_head *h)
+{
+ struct hlist_nulls_node *i, *last = NULL;
+
+ for (i = hlist_nulls_first_rcu(h); !is_a_nulls(i);
+ i = hlist_nulls_next_rcu(i))
+ last = i;
+
+ if (last) {
+ n->next = last->next;
+ n->pprev = &last->next;
+ rcu_assign_pointer(hlist_nulls_next_rcu(last), n);
+ } else {
+ hlist_nulls_add_head_rcu(n, h);
+ }
+}
+
/**
* hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type
* @tpos: the type * to use as a loop cursor.
diff --git a/include/net/sock.h b/include/net/sock.h
index 591d303..636476d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -631,7 +631,11 @@ static inline void sk_add_node_rcu(struct sock *sk, struct hlist_head *list)
static inline void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
{
- hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
+ if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&
+ sk->sk_family == AF_INET6)
+ hlist_nulls_add_tail_rcu(&sk->sk_nulls_node, list);
+ else
+ hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
}
static inline void sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 031752e..49afbe1 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -297,8 +297,13 @@ found:
hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
spin_lock(&hslot2->lock);
- hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
- &hslot2->head);
+ if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&
+ sk->sk_family == AF_INET6)
+ hlist_nulls_add_tail_rcu(&udp_sk(sk)->udp_portaddr_node,
+ &hslot2->head);
+ else
+ hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
+ &hslot2->head);
hslot2->count++;
spin_unlock(&hslot2->lock);
}
--
2.7.4
--
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