signal/cifs: Fix cifs_put_tcp_session to call send_sig instead of force_sig

stable inclusion
from linux-4.19.99
commit e6a13c753f912564256d81f7036f9c524b1ef8ae
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

[ Upstream commit 72abe3bc ]

The locking in force_sig_info is not prepared to deal with a task that
exits or execs (as sighand may change).  The is not a locking problem
in force_sig as force_sig is only built to handle synchronous
exceptions.

Further the function force_sig_info changes the signal state if the
signal is ignored, or blocked or if SIGNAL_UNKILLABLE will prevent the
delivery of the signal.  The signal SIGKILL can not be ignored and can
not be blocked and SIGNAL_UNKILLABLE won't prevent it from being
delivered.

So using force_sig rather than send_sig for SIGKILL is confusing
and pointless.

Because it won't impact the sending of the signal and and because
using force_sig is wrong, replace force_sig with send_sig.

Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Jeff Layton <jlayton@primarydata.com>
Cc: Steve French <smfrench@gmail.com>
Fixes: a5c3e1c7 ("Revert "cifs: No need to send SIGKILL to demux_thread during umount"")
Fixes: e7ddee90 ("cifs: disable sharing session and tcon and add new TCP sharing code")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
[io_uring need allow_kernel_signal]
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

fs/cifs/connect.c

@@ -2458,7 +2458,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 
 	task = xchg(&server->tsk, NULL);
 	if (task)
-		force_sig(SIGKILL, task);
+		send_sig(SIGKILL, task, 1);
 }
 
 static struct TCP_Server_Info *