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Message-Id: <20191211170943.134769-1-edumazet@google.com>
Date: Wed, 11 Dec 2019 09:09:43 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Michal Kubecek <mkubecek@...e.cz>,
Firo Yang <firo.yang@...e.com>
Subject: [PATCH net] tcp/dccp: fix possible race __inet_lookup_established()
Michal Kubecek and Firo Yang did a very nice analysis of crashes
happening in __inet_lookup_established().
Since a TCP socket can go from TCP_ESTABLISH to TCP_LISTEN
(via a close()/socket()/listen() cycle) without a RCU grace period,
I should not have changed listeners linkage in their hash table.
They must use the nulls protocol (Documentation/RCU/rculist_nulls.txt),
so that a lookup can detect a socket in a hash list was moved in
another one.
Since we added code in commit d296ba60d8e2 ("soreuseport: Resolve
merge conflict for v4/v6 ordering fix"), we have to add
hlist_nulls_add_tail_rcu() helper.
Fixes: 3b24d854cb35 ("tcp/dccp: do not touch listener sk_refcnt under synflood")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Michal Kubecek <mkubecek@...e.cz>
Reported-by: Firo Yang <firo.yang@...e.com>
Link: https://lore.kernel.org/netdev/20191120083919.GH27852@unicorn.suse.cz/
---
include/linux/rculist_nulls.h | 37 +++++++++++++++++++++++++++++++++++
include/net/inet_hashtables.h | 11 +++++++++--
include/net/sock.h | 5 +++++
net/ipv4/inet_diag.c | 3 ++-
net/ipv4/inet_hashtables.c | 16 +++++++--------
net/ipv4/tcp_ipv4.c | 7 ++++---
6 files changed, 65 insertions(+), 14 deletions(-)
diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h
index bc8206a8f30e6b0c2172e3bc3da3a85cab536cdd..61974c4c566be44af05531ce5b53040d586153a0 100644
--- a/include/linux/rculist_nulls.h
+++ b/include/linux/rculist_nulls.h
@@ -100,6 +100,43 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
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 specified hlist_nulls,
+ * while permitting racing traversals.
+ *
+ * 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;
+
+ /* Note: write side code, so rcu accessors are not needed. */
+ for (i = h->first; !is_a_nulls(i); i = i->next)
+ last = i;
+
+ if (last) {
+ n->next = last->next;
+ n->pprev = &last->next;
+ rcu_assign_pointer(hlist_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/inet_hashtables.h b/include/net/inet_hashtables.h
index af2b4c065a042e36135fe6fdcee9833b6b353364..29ef5b7f4005a8e67fd358c136ee6532974efcab 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -105,11 +105,18 @@ struct inet_bind_hashbucket {
/*
* Sockets can be hashed in established or listening table
- */
+ * We must use different 'nulls' end-of-chain value for listening
+ * hash table, or we might find a socket that was closed and
+ * reallocated/inserted into established hash table
+ */
+#define LISTENING_NULLS_BASE (1U << 29)
struct inet_listen_hashbucket {
spinlock_t lock;
unsigned int count;
- struct hlist_head head;
+ union {
+ struct hlist_head head;
+ struct hlist_nulls_head nulls_head;
+ };
};
/* This is for listening sockets, thus all sockets which possess wildcards. */
diff --git a/include/net/sock.h b/include/net/sock.h
index 87d54ef57f0040fd7bbd4344db0d3af7e6f6d992..04c274a20620b8d6a9d2118060ef0090f768bd60 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -722,6 +722,11 @@ static inline void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_h
hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
}
+static inline void __sk_nulls_add_node_tail_rcu(struct sock *sk, struct hlist_nulls_head *list)
+{
+ hlist_nulls_add_tail_rcu(&sk->sk_nulls_node, list);
+}
+
static inline void sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
{
sock_hold(sk);
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index af154977904c0c249e77e425990a09c62cca4251..f11e997e517b6652479acd892ffea6cdeb940e33 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -911,11 +911,12 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb,
for (i = s_i; i < INET_LHTABLE_SIZE; i++) {
struct inet_listen_hashbucket *ilb;
+ struct hlist_nulls_node *node;
num = 0;
ilb = &hashinfo->listening_hash[i];
spin_lock(&ilb->lock);
- sk_for_each(sk, &ilb->head) {
+ sk_nulls_for_each(sk, node, &ilb->nulls_head) {
struct inet_sock *inet = inet_sk(sk);
if (!net_eq(sock_net(sk), net))
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 83fb00153018f16678e71695134f7ae4d30ee0a3..2bbaaf0c717634502aa64098d1f4581b3eb1207d 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -516,10 +516,11 @@ static int inet_reuseport_add_sock(struct sock *sk,
struct inet_listen_hashbucket *ilb)
{
struct inet_bind_bucket *tb = inet_csk(sk)->icsk_bind_hash;
+ const struct hlist_nulls_node *node;
struct sock *sk2;
kuid_t uid = sock_i_uid(sk);
- sk_for_each_rcu(sk2, &ilb->head) {
+ sk_nulls_for_each_rcu(sk2, node, &ilb->nulls_head) {
if (sk2 != sk &&
sk2->sk_family == sk->sk_family &&
ipv6_only_sock(sk2) == ipv6_only_sock(sk) &&
@@ -555,9 +556,9 @@ int __inet_hash(struct sock *sk, struct sock *osk)
}
if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&
sk->sk_family == AF_INET6)
- hlist_add_tail_rcu(&sk->sk_node, &ilb->head);
+ __sk_nulls_add_node_tail_rcu(sk, &ilb->nulls_head);
else
- hlist_add_head_rcu(&sk->sk_node, &ilb->head);
+ __sk_nulls_add_node_rcu(sk, &ilb->nulls_head);
inet_hash2(hashinfo, sk);
ilb->count++;
sock_set_flag(sk, SOCK_RCU_FREE);
@@ -606,11 +607,9 @@ void inet_unhash(struct sock *sk)
reuseport_detach_sock(sk);
if (ilb) {
inet_unhash2(hashinfo, sk);
- __sk_del_node_init(sk);
- ilb->count--;
- } else {
- __sk_nulls_del_node_init_rcu(sk);
+ ilb->count--;
}
+ __sk_nulls_del_node_init_rcu(sk);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
unlock:
spin_unlock_bh(lock);
@@ -750,7 +749,8 @@ void inet_hashinfo_init(struct inet_hashinfo *h)
for (i = 0; i < INET_LHTABLE_SIZE; i++) {
spin_lock_init(&h->listening_hash[i].lock);
- INIT_HLIST_HEAD(&h->listening_hash[i].head);
+ INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].nulls_head,
+ i + LISTENING_NULLS_BASE);
h->listening_hash[i].count = 0;
}
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 92282f98dc82290bfaf53acc050182e4cc3be1eb..1c7326e04f9bee463500e17ea7c6eb840a31d89f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2147,13 +2147,14 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
struct tcp_iter_state *st = seq->private;
struct net *net = seq_file_net(seq);
struct inet_listen_hashbucket *ilb;
+ struct hlist_nulls_node *node;
struct sock *sk = cur;
if (!sk) {
get_head:
ilb = &tcp_hashinfo.listening_hash[st->bucket];
spin_lock(&ilb->lock);
- sk = sk_head(&ilb->head);
+ sk = sk_nulls_head(&ilb->nulls_head);
st->offset = 0;
goto get_sk;
}
@@ -2161,9 +2162,9 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
++st->num;
++st->offset;
- sk = sk_next(sk);
+ sk = sk_nulls_next(sk);
get_sk:
- sk_for_each_from(sk) {
+ sk_nulls_for_each_from(sk, node) {
if (!net_eq(sock_net(sk), net))
continue;
if (sk->sk_family == afinfo->family)
--
2.24.0.525.g8f36a354ae-goog
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