linux-kernel - [PATCH v2 05/19] fbdev/sysfs: Fix locking

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Message-Id: <20220208210824.2238981-6-daniel.vetter@ffwll.ch>
Date:   Tue,  8 Feb 2022 22:08:10 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        linux-fbdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Helge Deller <deller@....de>, Daniel Vetter <daniel@...ll.ch>,
        Qing Wang <wangqing@...o.com>
Subject: [PATCH v2 05/19] fbdev/sysfs: Fix locking

fb_set_var requires we hold the fb_info lock. Or at least this now
matches what the ioctl does ...

Note that ps3fb and sh_mobile_lcdcfb are busted in different ways here,
but I will not fix them up.

Also in practice this isn't a big deal, because really variable fbdev
state is actually protected by console_lock (because fbcon just
doesn't bother with lock_fb_info() at all), and lock_fb_info
protecting anything is really just a neat lie. But that's a much
bigger fish to fry.

Acked-by: Sam Ravnborg <sam@...nborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Cc: Helge Deller <deller@....de>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: Qing Wang <wangqing@...o.com>
Cc: Sam Ravnborg <sam@...nborg.org>
---
 drivers/video/fbdev/core/fbsysfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c
index 26892940c213..8c1ee9ecec3d 100644
--- a/drivers/video/fbdev/core/fbsysfs.c
+++ b/drivers/video/fbdev/core/fbsysfs.c
@@ -91,9 +91,11 @@ static int activate(struct fb_info *fb_info, struct fb_var_screeninfo *var)
 
 	var->activate |= FB_ACTIVATE_FORCE;
 	console_lock();
+	lock_fb_info(fb_info);
 	err = fb_set_var(fb_info, var);
 	if (!err)
 		fbcon_update_vcs(fb_info, var->activate & FB_ACTIVATE_ALL);
+	unlock_fb_info(fb_info);
 	console_unlock();
 	if (err)
 		return err;
-- 
2.34.1