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bpf, sock_map: Move cancel_work_sync() out of sock lock

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Stanislav reported a lockdep warning, which is caused by the
cancel_work_sync() called inside sock_map_close(), as analyzed
below by Jakub:

psock->work.func = sk_psock_backlog()
  ACQUIRE psock->work_mutex
    sk_psock_handle_skb()
      skb_send_sock()
        __skb_send_sock()
          sendpage_unlocked()
            kernel_sendpage()
              sock->ops->sendpage = inet_sendpage()
                sk->sk_prot->sendpage = tcp_sendpage()
                  ACQUIRE sk->sk_lock
                    tcp_sendpage_locked()
                  RELEASE sk->sk_lock
  RELEASE psock->work_mutex

sock_map_close()
  ACQUIRE sk->sk_lock
  sk_psock_stop()
    sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED)
    cancel_work_sync()
      __cancel_work_timer()
        __flush_work()
          // wait for psock->work to finish
  RELEASE sk->sk_lock

We can move the cancel_work_sync() out of the sock lock protection,
but still before saved_close() was called.

Fixes: 799aa7f98d ("skmsg: Avoid lock_sock() in sk_psock_backlog()")
Reported-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20221102043417.279409-1-xiyou.wangcong@gmail.com
This commit is contained in:
Cong Wang
2022-11-01 21:34:17 -07:00
committed by Daniel Borkmann
parent a778f5d46b
commit 8bbabb3fdd
3 changed files with 7 additions and 9 deletions
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2
include/linux/skmsg.h
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@@ -376,7 +376,7 @@ static inline void sk_psock_report_error(struct sk_psock *psock, int err)
}
struct sk_psock *sk_psock_init(struct sock *sk, int node);
void sk_psock_stop(struct sk_psock *psock, bool wait);
void sk_psock_stop(struct sk_psock *psock);
#if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
int sk_psock_init_strp(struct sock *sk, struct sk_psock *psock);