From: Jiang Liu Date: Thu, 6 Jun 2013 16:07:23 +0000 (+0800) Subject: zram: use zram->lock to protect zram_free_page() in swap free notify path X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=57ab048532c0d975538cebd4456491b5c34248f4;p=linux-beck.git zram: use zram->lock to protect zram_free_page() in swap free notify path zram_slot_free_notify() is free-running without any protection from concurrent operations. So there are race conditions between zram_bvec_read()/zram_bvec_write() and zram_slot_free_notify(), and possible consequences include: 1) Trigger BUG_ON(!handle) on zram_bvec_write() side. 2) Access to freed pages on zram_bvec_read() side. 3) Break some fields (bad_compress, good_compress, pages_stored) in zram->stats if the swap layer makes concurrently call to zram_slot_free_notify(). So enhance zram_slot_free_notify() to acquire writer lock on zram->lock before calling zram_free_page(). Signed-off-by: Jiang Liu Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 9057520c0e40..8d12e803aa0a 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -582,7 +582,9 @@ static void zram_slot_free_notify(struct block_device *bdev, struct zram *zram; zram = bdev->bd_disk->private_data; + down_write(&zram->lock); zram_free_page(zram, index); + up_write(&zram->lock); zram_stat64_inc(zram, &zram->stats.notify_free); } diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h index 2d1a3f1e8edb..d542eee81357 100644 --- a/drivers/staging/zram/zram_drv.h +++ b/drivers/staging/zram/zram_drv.h @@ -93,8 +93,9 @@ struct zram_meta { struct zram { struct zram_meta *meta; spinlock_t stat64_lock; /* protect 64-bit stats */ - struct rw_semaphore lock; /* protect compression buffers and table - * against concurrent read and writes */ + struct rw_semaphore lock; /* protect compression buffers, table, + * 32bit stat counters against concurrent + * notifications, reads and writes */ struct request_queue *queue; struct gendisk *disk; int init_done;