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/console/fbcon.c b/drivers/video/console/fbcon.c
index 1657b96..2cd500a 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -2954,8 +2954,11 @@
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 @@
}
}
- 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 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 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 @@
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 @@
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 @@
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;
}