This is a note to let you know that I've just added the patch titled
zram: use zram->lock to protect zram_free_page() in swap free notify path
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
zram-use-zram-lock-to-protect-zram_free_page-in-swap-free-notify-path.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 57ab048532c0d975538cebd4456491b5c34248f4 Mon Sep 17 00:00:00 2001
From: Jiang Liu <[email protected]>
Date: Fri, 7 Jun 2013 00:07:23 +0800
Subject: zram: use zram->lock to protect zram_free_page() in swap free notify
path
From: Jiang Liu <[email protected]>
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 <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/staging/zram/zram_drv.c | 2 ++
drivers/staging/zram/zram_drv.h | 5 +++--
2 files changed, 5 insertions(+), 2 deletions(-)
--- 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
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);
}
--- 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;
Patches currently in stable-queue which might be from [email protected] are
queue-3.10/zram-avoid-access-beyond-the-zram-device.patch
queue-3.10/zram-protect-sysfs-handler-from-invalid-memory-access.patch
queue-3.10/zram-avoid-double-free-in-function-zram_bvec_write.patch
queue-3.10/zram-use-zram-lock-to-protect-zram_free_page-in-swap-free-notify-path.patch
queue-3.10/zram-avoid-invalid-memory-access-in-zram_exit.patch
queue-3.10/zram-destroy-all-devices-on-error-recovery-path-in-zram_init.patch
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