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Subject[patch 002/100] fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Andrea Righi <righi.andrea@gmail.com>

upstream commit: 66c1ca019078220dc1bf968f2bb18421100ef147

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>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
drivers/video/backlight/backlight.c | 3 +
drivers/video/backlight/lcd.c | 3 +
drivers/video/console/fbcon.c | 73 +++++++++++++++++++++++++++++++-----
drivers/video/fbmem.c | 11 -----
4 files changed, 70 insertions(+), 20 deletions(-)

--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -35,6 +35,8 @@ static int fb_notifier_callback(struct n
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 n
backlight_update_status(bd);
}
mutex_unlock(&bd->ops_lock);
+ unlock_fb_info(evdata->info);
return 0;
}

--- a/drivers/video/backlight/lcd.c
+++ b/drivers/video/backlight/lcd.c
@@ -40,6 +40,8 @@ static int fb_notifier_callback(struct n
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 n
}
}
mutex_unlock(&ld->ops_lock);
+ unlock_fb_info(evdata->info);
return 0;
}

--- 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
}
}

- 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(

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
}
}

-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 not
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 not

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 not
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;
}
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1086,13 +1086,8 @@ static long do_fb_ioctl(struct fb_info *
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 *
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))


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