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tcp: Migrate TCP_ESTABLISHED/TCP_SYN_RECV sockets in accept queues.

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When we call close() or shutdown() for listening sockets, each child socket
in the accept queue are freed at inet_csk_listen_stop(). If we can get a
new listener by reuseport_migrate_sock() and clone the request by
inet_reqsk_clone(), we try to add it into the new listener's accept queue
by inet_csk_reqsk_queue_add(). If it fails, we have to call __reqsk_free()
to call sock_put() for its listener and free the cloned request.

After putting the full socket into ehash, tcp_v[46]_syn_recv_sock() sets
NULL to ireq_opt/pktopts in struct inet_request_sock, but ipv6_opt can be
non-NULL. So, we have to set NULL to ipv6_opt of the old request to avoid
double free.

Note that we do not update req->rsk_listener and instead clone the req to
migrate because another path may reference the original request. If we
protected it by RCU, we would need to add rcu_read_lock() in many places.

Suggested-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/netdev/20201209030903.hhow5r53l6fmozjn@kafai-mbp.dhcp.thefacebook.com/
Link: https://lore.kernel.org/bpf/20210612123224.12525-6-kuniyu@amazon.co.jp
This commit is contained in:
Kuniyuki Iwashima 2021-06-12 21:32:18 +09:00 committed by Daniel Borkmann
parent 1cd62c2157
commit 54b92e8419
1 changed files with 69 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

70
net/ipv4/inet_connection_sock.c
View File

@ -695,6 +695,52 @@ int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req)
}
EXPORT_SYMBOL(inet_rtx_syn_ack);
static struct request_sock *inet_reqsk_clone(struct request_sock *req,
struct sock *sk)
{
struct sock *req_sk, *nreq_sk;
struct request_sock *nreq;
nreq = kmem_cache_alloc(req->rsk_ops->slab, GFP_ATOMIC | __GFP_NOWARN);
if (!nreq) {
/* paired with refcount_inc_not_zero() in reuseport_migrate_sock() */
sock_put(sk);
return NULL;
}
req_sk = req_to_sk(req);
nreq_sk = req_to_sk(nreq);
memcpy(nreq_sk, req_sk,
offsetof(struct sock, sk_dontcopy_begin));
memcpy(&nreq_sk->sk_dontcopy_end, &req_sk->sk_dontcopy_end,
req->rsk_ops->obj_size - offsetof(struct sock, sk_dontcopy_end));
sk_node_init(&nreq_sk->sk_node);
nreq_sk->sk_tx_queue_mapping = req_sk->sk_tx_queue_mapping;
#ifdef CONFIG_XPS
nreq_sk->sk_rx_queue_mapping = req_sk->sk_rx_queue_mapping;
#endif
nreq_sk->sk_incoming_cpu = req_sk->sk_incoming_cpu;
nreq->rsk_listener = sk;
/* We need not acquire fastopenq->lock
* because the child socket is locked in inet_csk_listen_stop().
*/
if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(nreq)->tfo_listener)
rcu_assign_pointer(tcp_sk(nreq->sk)->fastopen_rsk, nreq);
return nreq;
}
static void reqsk_migrate_reset(struct request_sock *req)
{
#if IS_ENABLED(CONFIG_IPV6)
inet_rsk(req)->ipv6_opt = NULL;
#endif
}
/* return true if req was found in the ehash table */
static bool reqsk_queue_unlink(struct request_sock *req)
{
@ -1036,14 +1082,36 @@ void inet_csk_listen_stop(struct sock *sk)
* of the variants now. --ANK
*/
while ((req = reqsk_queue_remove(queue, sk)) != NULL) {
struct sock *child = req->sk;
struct sock *child = req->sk, *nsk;
struct request_sock *nreq;
local_bh_disable();
bh_lock_sock(child);
WARN_ON(sock_owned_by_user(child));
sock_hold(child);
nsk = reuseport_migrate_sock(sk, child, NULL);
if (nsk) {
nreq = inet_reqsk_clone(req, nsk);
if (nreq) {
refcount_set(&nreq->rsk_refcnt, 1);
if (inet_csk_reqsk_queue_add(nsk, nreq, child)) {
reqsk_migrate_reset(req);
} else {
reqsk_migrate_reset(nreq);
__reqsk_free(nreq);
}
/* inet_csk_reqsk_queue_add() has already
* called inet_child_forget() on failure case.
*/
goto skip_child_forget;
}
}
inet_child_forget(sk, req, child);
skip_child_forget:
reqsk_put(req);
bh_unlock_sock(child);
local_bh_enable();