tcp: fix memleak when tcp internal pacing is used

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4S8PN
CVE: NA

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The sock_hold() in tcp_internal_pacing() is expected to pair with
sock_put() in tcp_pace_kick(). But in some path tcp_internal_pacing()
is called without checking if pacing timer is already armed, causing
sock_hold() to be called one more time and tcp sock can't be released.

As Neal pointed out, this could happen from some of the retransmission
code paths that don't use tcp_xmit_retransmit_queue(), such as
tcp_retransmit_timer() and tcp_send_loss_probe().

The fix is provided by Eric, it extends the timer to cover all these
points that Neal mentioned.

Following is the reproduce procedure provided by Jason:
0) cat /proc/slabinfo | grep TCP
1) switch net.ipv4.tcp_congestion_control to bbr
2) using wrk tool something like that to send packages
3) using tc to increase the delay and loss to simulate the RTO case.
4) cat /proc/slabinfo | grep TCP
5) kill the wrk command and observe the number of objects and slabs in
TCP.
6) at last, you could notice that the number would not decrease.

Link: https://lore.kernel.org/all/CANn89i+7-wE4xr5D9DpH+N-xkL1SB8oVghCKgz+CT5eG1ODQhA@mail.gmail.com/


Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>