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authorAndrea Righi <righi.andrea@gmail.com>2009-03-31 15:25:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-01 08:59:29 -0700
commit66c1ca019078220dc1bf968f2bb18421100ef147 (patch)
treeb01d28d74bab9d9e3f0f24841a80a272d6f6520a /drivers/video/backlight/lcd.c
parent8636a9240cc93efa6b36f4cfe6253e0574f832c6 (diff)
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>
Diffstat (limited to 'drivers/video/backlight/lcd.c')
-rw-r--r--drivers/video/backlight/lcd.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/video/backlight/lcd.c b/drivers/video/backlight/lcd.c
index b6449470106c..0bb13df0fa89 100644
--- 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;
}