fbdev: fix info->lock deadlock in fbcon_event_notify()

fb_notifier_call_chain() is called with info->lock held, i.e.  in
do_fb_ioctl() => FBIOPUT_VSCREENINFO => fb_set_var() and the some
notifier callbacks, like fbcon_event_notify(), try to re-acquire
info->lock again.

Remove the lock/unlock_fb_info() in all the framebuffer notifier
callbacks' and be sure to always call fb_notifier_call_chain() with
info->lock held.

Reported-by: Pavel Roskin <proski@gnu.org>
Reported-by: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 52 deletions

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 2cd500a304f..471a9a60376 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -2263,9 +2263,12 @@ static void fbcon_generic_blank(struct vc_data *vc, struct fb_info *info,
 	}
 
 
+	if (!lock_fb_info(info))
+		return;
 	event.info = info;
 	event.data = ␣
 	fb_notifier_call_chain(FB_EVENT_CONBLANK, &event);
+	unlock_fb_info(info);
 }
 
 static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
@@ -2956,8 +2959,6 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 {
 	int i, idx;
 
-	if (!lock_fb_info(info))
-		return -ENODEV;
 	idx = info->node;
 	for (i = first_fb_vc; i <= last_fb_vc; i++) {
 		if (con2fb_map[i] == idx)
@@ -2985,8 +2986,6 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 	if (primary_device == idx)
 		primary_device = -1;
 
-	unlock_fb_info(info);
-
 	if (!num_registered_fb)
 		unregister_con_driver(&fb_con);
 
@@ -3027,11 +3026,8 @@ static int fbcon_fb_registered(struct fb_info *info)
 {
 	int ret = 0, i, idx;
 
-	if (!lock_fb_info(info))
-		return -ENODEV;
 	idx = info->node;
 	fbcon_select_primary(info);
-	unlock_fb_info(info);
 
 	if (info_idx == -1) {
 		for (i = first_fb_vc; i <= last_fb_vc; i++) {
@@ -3152,53 +3148,23 @@ static int fbcon_event_notify(struct notifier_block *self,
 
 	switch(action) {
 	case FB_EVENT_SUSPEND:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_suspended(info);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_RESUME:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_resumed(info);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_MODE_CHANGE:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_modechanged(info);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_MODE_CHANGE_ALL:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_set_all_vcs(info);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_MODE_DELETE:
 		mode = event->data;
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		ret = fbcon_mode_deleted(info, mode);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_FB_UNBIND:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		idx = info->node;
-		unlock_fb_info(info);
 		ret = fbcon_fb_unbind(idx);
 		break;
 	case FB_EVENT_FB_REGISTERED:
@@ -3217,29 +3183,14 @@ static int fbcon_event_notify(struct notifier_block *self,
 		con2fb->framebuffer = con2fb_map[con2fb->console - 1];
 		break;
 	case FB_EVENT_BLANK:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_fb_blanked(info, *(int *)event->data);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_NEW_MODELIST:
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_new_modelist(info);
-		unlock_fb_info(info);
 		break;
 	case FB_EVENT_GET_REQ:
 		caps = event->data;
-		if (!lock_fb_info(info)) {
-			ret = -ENODEV;
-			goto done;
-		}
 		fbcon_get_requirement(info, caps);
-		unlock_fb_info(info);
 		break;
 	}
 done: