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Date: Sun, 22 Mar 2009 14:52:19 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: "Rafael J. Wysocki" <rjw@...k.pl>
Cc: Andrey Borzenkov <arvidjaar@...il.com>,
Andrea Righi <righi.andrea@...il.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
"Antonino A. Daplas" <adaplas@...il.com>,
linux-fbdev-devel@...ts.sourceforge.net,
linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
Dave Jones <davej@...hat.com>,
Harvey Harrison <harvey.harrison@...il.com>,
Johannes Weiner <hannes@...xchg.org>,
Stefan Richter <stefanr@...6.in-berlin.de>,
Krzysztof Helt <krzysztof.h1@...zta.fm>
Subject: Re: [PATCH -mmotm] fbmem: fix fb_info->lock and mm->mmap_sem
circular locking dependency
On Sun, 22 Mar 2009 18:57:19 +0100 "Rafael J. Wysocki" <rjw@...k.pl> wrote:
> On Sunday 22 March 2009, Andrey Borzenkov wrote:
> > On 5 ______________ 2009 00:46:23 Andrea Righi wrote:
> > > Fix this circular locking dependencies 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@...l.ru>
> > > Signed-off-by: Andrea Righi <righi.andrea@...il.com>
> >
> > Hmm ... is it in current Linus tree? Because I happened to have this again
> > in rc8:
>
> It doesn't seems so, at least I don't see it in there.
I didn't realise that this was needed in mainline.
I would hate to mrege it this late and find that it introduces some nasty
new deadlock which everyone hits. Probably it's more prodent to merge it
into 2.6.29.1 now.
From: Andrea Righi <righi.andrea@...il.com>
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@...l.ru>
Signed-off-by: Andrea Righi <righi.andrea@...il.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Krzysztof Helt <krzysztof.h1@...zta.fm>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.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(-)
diff -puN drivers/video/backlight/backlight.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/backlight/backlight.c
--- a/drivers/video/backlight/backlight.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/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;
}
diff -puN drivers/video/backlight/lcd.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/backlight/lcd.c
--- a/drivers/video/backlight/lcd.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/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;
}
diff -puN drivers/video/console/fbcon.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/console/fbcon.c
--- a/drivers/video/console/fbcon.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/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;
}
diff -puN drivers/video/fbmem.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/fbmem.c
--- a/drivers/video/fbmem.c~fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/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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