fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency

Fix a circular locking dependency in the frame buffer console driver
pushing down the mutex fb_info->lock.

Circular locking dependecies occur calling the blocking
fb_notifier_call_chain() with fb_info->lock held.  Notifier callbacks can
try to acquire mm->mmap_sem, while fb_mmap() acquires the locks in the
reverse order mm->mmap_sem => fb_info->lock.

Tested-by: Andrey Borzenkov <arvidjaar@mail.ru>
Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 157057c..dd37cbc 100644 (file)
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -35,6 +35,8 @@ static int fb_notifier_callback(struct notifier_block *self,
                return 0;
 
        bd = container_of(self, struct backlight_device, fb_notif);
+       if (!lock_fb_info(evdata->info))
+               return -ENODEV;
        mutex_lock(&bd->ops_lock);
        if (bd->ops)
                if (!bd->ops->check_fb ||
@@ -47,6 +49,7 @@ static int fb_notifier_callback(struct notifier_block *self,
                        backlight_update_status(bd);
                }
        mutex_unlock(&bd->ops_lock);
+       unlock_fb_info(evdata->info);
        return 0;
 }
 

diff --git a/drivers/video/backlight/lcd.c b/drivers/video/backlight/lcd.c
index b644947..0bb13df 100644 (file)
--- a/drivers/video/backlight/lcd.c
+++ b/drivers/video/backlight/lcd.c
@@ -40,6 +40,8 @@ static int fb_notifier_callback(struct notifier_block *self,
        if (!ld->ops)
                return 0;
 
+       if (!lock_fb_info(evdata->info))
+               return -ENODEV;
        mutex_lock(&ld->ops_lock);
        if (!ld->ops->check_fb || ld->ops->check_fb(ld, evdata->info)) {
                if (event == FB_EVENT_BLANK) {
@@ -51,6 +53,7 @@ static int fb_notifier_callback(struct notifier_block *self,
                }
        }
        mutex_unlock(&ld->ops_lock);
+       unlock_fb_info(evdata->info);
        return 0;
 }
 

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 1657b96..2cd500a 100644 (file)
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -2954,8 +2954,11 @@ static int fbcon_fb_unbind(int idx)
 
 static int fbcon_fb_unregistered(struct fb_info *info)
 {
-       int i, idx = info->node;
+       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)
                        con2fb_map[i] = -1;
@@ -2979,13 +2982,14 @@ static int fbcon_fb_unregistered(struct fb_info *info)
                }
        }
 
-       if (!num_registered_fb)
-               unregister_con_driver(&fb_con);
-
-
        if (primary_device == idx)
                primary_device = -1;
 
+       unlock_fb_info(info);
+
+       if (!num_registered_fb)
+               unregister_con_driver(&fb_con);
+
        return 0;
 }
 
@@ -3021,9 +3025,13 @@ static inline void fbcon_select_primary(struct fb_info *info)
 
 static int fbcon_fb_registered(struct fb_info *info)
 {
-       int ret = 0, i, idx = info->node;
+       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++) {
@@ -3124,7 +3132,7 @@ static void fbcon_get_requirement(struct fb_info *info,
        }
 }
 
-static int fbcon_event_notify(struct notifier_block *self, 
+static int fbcon_event_notify(struct notifier_block *self,
                              unsigned long action, void *data)
 {
        struct fb_event *event = data;
@@ -3132,7 +3140,7 @@ static int fbcon_event_notify(struct notifier_block *self,
        struct fb_videomode *mode;
        struct fb_con2fbmap *con2fb;
        struct fb_blit_caps *caps;
-       int ret = 0;
+       int idx, ret = 0;
 
        /*
         * ignore all events except driver registration and deregistration
@@ -3144,23 +3152,54 @@ 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:
-               ret = fbcon_fb_unbind(info->node);
+               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:
                ret = fbcon_fb_registered(info);
@@ -3178,17 +3217,31 @@ 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:
        return ret;
 }

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index cfd9dce..b64f061 100644 (file)
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1086,13 +1086,8 @@ 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:
@@ -1109,12 +1104,8 @@ 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);
+               ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP, &event);
                break;
        case FBIOBLANK:
                if (!lock_fb_info(info))