linux-kernel - [PATCH 1/7] zram: fix race between reset and flushing pending work

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Date:	Mon, 13 Jan 2014 20:18:56 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	stable <stable@...r.kernel.org>
Subject: [PATCH 1/7] zram: fix race between reset and flushing pending work

Dan and Sergey reported that there is a racy between reset and
flushing of pending work so that it could make oops by freeing
zram->meta in reset while zram_slot_free can access zram->meta
if new request is adding during the race window.

This patch moves flush after taking init_lock so it prevents
new request so that it closes the race.

Cc: stable <stable@...r.kernel.org>
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 drivers/block/zram/zram_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f9711c5..213dfc1 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -553,14 +553,14 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
 	size_t index;
 	struct zram_meta *meta;
 
-	flush_work(&zram->free_work);
-
 	down_write(&zram->init_lock);
 	if (!zram->init_done) {
 		up_write(&zram->init_lock);
 		return;
 	}
 
+	flush_work(&zram->free_work);
+
 	meta = zram->meta;
 	zram->init_done = 0;
 
-- 
1.8.4.3

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