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, 19 insertions, 0 deletions

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 2ac32e6b5953..d412a1ddc12f 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1097,8 +1097,11 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
                         return -EINVAL;
                 con2fb.framebuffer = -1;
                 event.data = &con2fb;
+                if (!lock_fb_info(info))
+                        return -ENODEV;
                 event.info = info;
                 fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event);
+                unlock_fb_info(info);
                 ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0;
                 break;
         case FBIOPUT_CON2FBMAP:
@@ -1115,8 +1118,11 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
                         break;
                 }
                 event.data = &con2fb;
+                if (!lock_fb_info(info))
+                        return -ENODEV;
                 event.info = info;
                 ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP, &event);
+                unlock_fb_info(info);
                 break;
         case FBIOBLANK:
                 if (!lock_fb_info(info))
@@ -1521,7 +1527,10 @@ register_framebuffer(struct fb_info *fb_info)
         registered_fb[i] = fb_info;
 
         event.info = fb_info;
+        if (!lock_fb_info(fb_info))
+                return -ENODEV;
         fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);
+        unlock_fb_info(fb_info);
         return 0;
 }
 
@@ -1555,8 +1564,12 @@ unregister_framebuffer(struct fb_info *fb_info)
                 goto done;
         }
 
+
+        if (!lock_fb_info(fb_info))
+                return -ENODEV;
         event.info = fb_info;
         ret = fb_notifier_call_chain(FB_EVENT_FB_UNBIND, &event);
+        unlock_fb_info(fb_info);
 
         if (ret) {
                 ret = -EINVAL;
@@ -1590,6 +1603,8 @@ void fb_set_suspend(struct fb_info *info, int state)
 {
         struct fb_event event;
 
+        if (!lock_fb_info(info))
+                return;
         event.info = info;
         if (state) {
                 fb_notifier_call_chain(FB_EVENT_SUSPEND, &event);
@@ -1598,6 +1613,7 @@ void fb_set_suspend(struct fb_info *info, int state)
                 info->state = FBINFO_STATE_RUNNING;
                 fb_notifier_call_chain(FB_EVENT_RESUME, &event);
         }
+        unlock_fb_info(info);
 }
 
 /**
@@ -1667,8 +1683,11 @@ int fb_new_modelist(struct fb_info *info)
         err = 1;
 
         if (!list_empty(&info->modelist)) {
+                if (!lock_fb_info(info))
+                        return -ENODEV;
                 event.info = info;
                 err = fb_notifier_call_chain(FB_EVENT_NEW_MODELIST, &event);
+                unlock_fb_info(info);
         }
 
         return err;