[PATCH 6.1 402/451] tcp: Fix NEW_SYN_RECV handling in inet_twsk_purge()

Sasha Levin
2024-03-24T23:18:39Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 1c4e97dd2d3c9a3e84f7e26346aa39bc426d3249 ]

inet_twsk_purge() uses rcu to find TIME_WAIT and NEW_SYN_RECV
objects to purge.

These objects use SLAB_TYPESAFE_BY_RCU semantic and need special
care. We need to use refcount_inc_not_zero(&sk->sk_refcnt).

Reuse the existing correct logic I wrote for TIME_WAIT,
because both structures have common locations for
sk_state, sk_family, and netns pointer.

If after the refcount_inc_not_zero() the object fields longer match
the keys, use sock_gen_put(sk) to release the refcount.

Then we can call inet_twsk_deschedule_put() for TIME_WAIT,
inet_csk_reqsk_queue_drop_and_put() for NEW_SYN_RECV sockets,
with BH disabled.

Then we need to restart the loop because we had drop rcu_read_lock().

Fixes: 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in inet_twsk_purge()")
Link: https://lore.kernel.org/netdev/CANn89iLvFuuihCtt9PME2uS1WJATnf5fKjDToa1WzVnRzHnPfg@mail.gmail.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240308200122.64357-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/inet_timewait_sock.c | 41 ++++++++++++++++-------------------
1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 1d77d992e6e77..340a8f0c29800 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -281,12 +281,12 @@ void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
}
EXPORT_SYMBOL_GPL(__inet_twsk_schedule);

+/* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
{
- struct inet_timewait_sock *tw;
- struct sock *sk;
struct hlist_nulls_node *node;
unsigned int slot;
+ struct sock *sk;

for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
@@ -295,38 +295,35 @@ void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
rcu_read_lock();
restart:
sk_nulls_for_each_rcu(sk, node, &head->chain) {
- if (sk->sk_state != TCP_TIME_WAIT) {
- /* A kernel listener socket might not hold refcnt for net,
- * so reqsk_timer_handler() could be fired after net is
- * freed. Userspace listener and reqsk never exist here.
- */
- if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV &&
- hashinfo->pernet)) {
- struct request_sock *req = inet_reqsk(sk);
-
- inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
- }
+ int state = inet_sk_state_load(sk);

+ if ((1 << state) & ~(TCPF_TIME_WAIT |
+ TCPF_NEW_SYN_RECV))
continue;
- }

- tw = inet_twsk(sk);
- if ((tw->tw_family != family) ||
- refcount_read(&twsk_net(tw)->ns.count))
+ if (sk->sk_family != family ||
+ refcount_read(&sock_net(sk)->ns.count))
continue;

- if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
+ if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
continue;

- if (unlikely((tw->tw_family != family) ||
- refcount_read(&twsk_net(tw)->ns.count))) {
- inet_twsk_put(tw);
+ if (unlikely(sk->sk_family != family ||
+ refcount_read(&sock_net(sk)->ns.count))) {
+ sock_gen_put(sk);
goto restart;
}

rcu_read_unlock();
local_bh_disable();
- inet_twsk_deschedule_put(tw);
+ if (state == TCP_TIME_WAIT) {
+ inet_twsk_deschedule_put(inet_twsk(sk));
+ } else {
+ struct request_sock *req = inet_reqsk(sk);
+
+ inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
+ req);
+ }
local_bh_enable();
goto restart_rcu;
}
--
2.43.0