linux-kernel - [PATCH 3.12 094/133] zram: fix race between reset and flushing pending work

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Message-Id: <20140204210739.688534746@linuxfoundation.org>
Date:	Tue,  4 Feb 2014 13:08:15 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Minchan Kim <minchan@...nel.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.12 094/133] zram: fix race between reset and flushing pending work

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Minchan Kim <minchan@...nel.org>

commit da4a04126baa3be03bc566d4a2ee0944c5e783d0 upstream.

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.

Signed-off-by: Minchan Kim <minchan@...nel.org>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Nitin Gupta <ngupta@...are.org>
Cc: Jerome Marchand <jmarchan@...hat.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/zram/zram_drv.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -552,14 +552,14 @@ static void zram_reset_device(struct zra
 	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;
 


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