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From:   "Eric W. Biederman" <ebiederm@xmission.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Wen Yang <wen.yang99@zte.com.cn>,
        majiang <ma.jiang@zte.com.cn>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Date:   Tue, 10 Jul 2018 21:44:57 -0500
Message-Id: <20180711024459.10654-9-ebiederm@xmission.com>
In-Reply-To: <877em2jxyr.fsf_-_@xmission.com>
References: <877em2jxyr.fsf_-_@xmission.com>
Subject: [RFC][PATCH 09/11] tty_io: Use do_send_sig_info in __do_SACK  to forcibly kill tasks
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

send_sig is thread only making it the wrong command for an action
         directed at a process.

force_sig does not set SEND_SIG_FORCED (causing unnecessary work in
	 __send_signal) and jumps through unnecessary hoops to deal
	 with blocked and ignored signals which SIGKILL can never be.

Therefore use do_send_sig_info in all cases in __do_SAK to kill
tasks as allows for exactly what the code wants to do.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 drivers/tty/tty_io.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index cec58c53b0c4..42ac168c2a47 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2747,7 +2747,7 @@ void __do_SAK(struct tty_struct *tty)
 	do_each_pid_task(session, PIDTYPE_SID, p) {
 		tty_notice(tty, "SAK: killed process %d (%s): by session\n",
 			   task_pid_nr(p), p->comm);
-		send_sig(SIGKILL, p, 1);
+		do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
 	} while_each_pid_task(session, PIDTYPE_SID, p);
 
 	/* Now kill any processes that happen to have the tty open */
@@ -2755,7 +2755,7 @@ void __do_SAK(struct tty_struct *tty)
 		if (p->signal->tty == tty) {
 			tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",
 				   task_pid_nr(p), p->comm);
-			send_sig(SIGKILL, p, 1);
+			do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
 			continue;
 		}
 		task_lock(p);
@@ -2763,7 +2763,7 @@ void __do_SAK(struct tty_struct *tty)
 		if (i != 0) {
 			tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
 				   task_pid_nr(p), p->comm, i - 1);
-			force_sig(SIGKILL, p);
+			do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
 		}
 		task_unlock(p);
 	} while_each_thread(g, p);
-- 
2.17.1