linux-kernel - [PATCH AUTOSEL 5.4 07/55] fbcon: Consistently protect deferred_takeover with console

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Date:   Mon, 30 May 2022 09:46:13 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Daniel Vetter <daniel@...ll.ch>, Du Cheng <ducheng2@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Claudio Suarez <cssk@...-c.es>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sasha Levin <sashal@...nel.org>, deller@....de,
        geert@...ux-m68k.org, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.4 07/55] fbcon: Consistently protect deferred_takeover with console_lock()

From: Daniel Vetter <daniel.vetter@...ll.ch>

[ Upstream commit 43553559121ca90965b572cf8a1d6d0fd618b449 ]

This shouldn't be a problem in practice since until we've actually
taken over the console there's nothing we've registered with the
console/vt subsystem, so the exit/unbind path that check this can't
do the wrong thing. But it's confusing, so fix it by moving it a tad
later.

Acked-by: Sam Ravnborg <sam@...nborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: Du Cheng <ducheng2@...il.com>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: Claudio Suarez <cssk@...-c.es>
Cc: Thomas Zimmermann <tzimmermann@...e.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220405210335.3434130-14-daniel.vetter@ffwll.ch
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/video/fbdev/core/fbcon.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 75b770514067..1decded4845f 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -3286,6 +3286,9 @@ static void fbcon_register_existing_fbs(struct work_struct *work)
 
 	console_lock();
 
+	deferred_takeover = false;
+	logo_shown = FBCON_LOGO_DONTSHOW;
+
 	for_each_registered_fb(i)
 		fbcon_fb_registered(registered_fb[i]);
 
@@ -3303,8 +3306,6 @@ static int fbcon_output_notifier(struct notifier_block *nb,
 	pr_info("fbcon: Taking over console\n");
 
 	dummycon_unregister_output_notifier(&fbcon_output_nb);
-	deferred_takeover = false;
-	logo_shown = FBCON_LOGO_DONTSHOW;
 
 	/* We may get called in atomic context */
 	schedule_work(&fbcon_deferred_takeover_work);
-- 
2.35.1