@@ -615,7 +615,9 @@ 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);
}
@@ -92,8 +92,9 @@ struct zram {
void *compress_buffer;
struct table *table;
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;
This is a note to let you know that I have just added a patch titled zram: use zram->lock to protect zram_free_page() in swap free to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From f56c0e44628257f97063089eb865d5eb2dfdd642 Mon Sep 17 00:00:00 2001 From: Jiang Liu <liuj97@gmail.com> Date: Fri, 7 Jun 2013 00:07:23 +0800 Subject: [PATCH] zram: use zram->lock to protect zram_free_page() in swap free notify path commit 57ab048532c0d975538cebd4456491b5c34248f4 upstream. 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 <jiang.liu@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [ luis: backported to 3.8: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/staging/zram/zram_drv.c | 2 ++ drivers/staging/zram/zram_drv.h | 5 +++-- 2 files changed, 5 insertions(+), 2 deletions(-) -- 1.8.1.2