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fbdev: fix info->lock deadlock in fbcon_event_notify()
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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>
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Andrea Righi authored and Linus Torvalds committed Apr 13, 2009
1 parent b52bb37 commit 513adb5
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Showing 4 changed files with 22 additions and 58 deletions.
3 changes: 0 additions & 3 deletions drivers/video/backlight/backlight.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,8 +35,6 @@ 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 ||
Expand All @@ -49,7 +47,6 @@ 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;
}

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3 changes: 0 additions & 3 deletions drivers/video/backlight/lcd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,6 @@ 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) {
Expand All @@ -53,7 +51,6 @@ static int fb_notifier_callback(struct notifier_block *self,
}
}
mutex_unlock(&ld->ops_lock);
unlock_fb_info(evdata->info);
return 0;
}

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55 changes: 3 additions & 52 deletions drivers/video/console/fbcon.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2263,9 +2263,12 @@ static void fbcon_generic_blank(struct vc_data *vc, struct fb_info *info,
}


if (!lock_fb_info(info))
return;
event.info = info;
event.data = &blank;
fb_notifier_call_chain(FB_EVENT_CONBLANK, &event);
unlock_fb_info(info);
}

static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
Expand Down Expand Up @@ -2956,8 +2959,6 @@ static int fbcon_fb_unregistered(struct fb_info *info)
{
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)
Expand Down Expand Up @@ -2985,8 +2986,6 @@ static int fbcon_fb_unregistered(struct fb_info *info)
if (primary_device == idx)
primary_device = -1;

unlock_fb_info(info);

if (!num_registered_fb)
unregister_con_driver(&fb_con);

Expand Down Expand Up @@ -3027,11 +3026,8 @@ static int fbcon_fb_registered(struct fb_info *info)
{
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++) {
Expand Down Expand Up @@ -3152,53 +3148,23 @@ 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:
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:
Expand All @@ -3217,29 +3183,14 @@ 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:
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19 changes: 19 additions & 0 deletions drivers/video/fbmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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:
Expand All @@ -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))
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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);
}

/**
Expand Down Expand Up @@ -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;
Expand Down

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