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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Namjae Jeon <namjae.jeon@samsung.com>,
        Jeff Layton <jlayton@primarydata.com>,
        Steve French <smfrench@gmail.com>,
        Sasha Levin <sashal@kernel.org>, linux-cifs@vger.kernel.org,
        samba-technical@lists.samba.org
Subject: [PATCH AUTOSEL 4.9 149/251] signal/cifs: Fix cifs_put_tcp_session to call send_sig instead of force_sig
Date:   Thu, 16 Jan 2020 12:34:58 -0500
Message-Id: <20200116173641.22137-109-sashal@kernel.org>
In-Reply-To: <20200116173641.22137-1-sashal@kernel.org>
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From: "Eric W. Biederman" <ebiederm@xmission.com>

[ Upstream commit 72abe3bcf0911d69b46c1e8bdb5612675e0ac42c ]

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: a5c3e1c725af ("Revert "cifs: No need to send SIGKILL to demux_thread during umount"")
Fixes: e7ddee9037e7 ("cifs: disable sharing session and tcon and add new TCP sharing code")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/connect.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index e43ba6db2bdd..110febd69737 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2221,7 +2221,7 @@ 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 *
-- 
2.20.1