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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Minh Yuan <yuanmingbuaa@gmail.com>,
        Jiri Slaby <jirislaby@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 4.14 19/23] vt_kdsetmode: extend console locking
Date:   Wed,  1 Sep 2021 14:27:04 +0200
Message-Id: <20210901122250.403697177@linuxfoundation.org>
In-Reply-To: <20210901122249.786673285@linuxfoundation.org>
References: <20210901122249.786673285@linuxfoundation.org>
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From: Linus Torvalds <torvalds@linux-foundation.org>

commit 2287a51ba822384834dafc1c798453375d1107c7 upstream.

As per the long-suffering comment.

Reported-by: Minh Yuan <yuanmingbuaa@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/vt/vt_ioctl.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -484,16 +484,19 @@ int vt_ioctl(struct tty_struct *tty,
 			ret = -EINVAL;
 			goto out;
 		}
-		/* FIXME: this needs the console lock extending */
-		if (vc->vc_mode == (unsigned char) arg)
+		console_lock();
+		if (vc->vc_mode == (unsigned char) arg) {
+			console_unlock();
 			break;
+		}
 		vc->vc_mode = (unsigned char) arg;
-		if (console != fg_console)
+		if (console != fg_console) {
+			console_unlock();
 			break;
+		}
 		/*
 		 * explicitly blank/unblank the screen if switching modes
 		 */
-		console_lock();
 		if (arg == KD_TEXT)
 			do_unblank_screen(1);
 		else