linux-kernel - [PATCH v2 08/10] zram: protect sysfs handler from invalid memory access

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Date:	Wed,  5 Jun 2013 00:06:06 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nitin Gupta <ngupta@...are.org>,
	Minchan Kim <minchan@...nel.org>,
	Jerome Marchand <jmarchan@...hat.com>
Cc:	Yijing Wang <wangyijing@...wei.com>,
	Jiang Liu <jiang.liu@...wei.com>, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 08/10] zram: protect sysfs handler from invalid memory access

Use zram->init_lock to protect access to zram->meta, otherwise it
may cause invalid memory access if zram->meta has been freed by
zram_reset_device().

This issue may be triggered by:
Thread 1:
while true; do cat mem_used_total; done
Thread 2:
while true; do echo 8M > disksize; echo 1 > reset; done

Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
Cc: stable@...r.kernel.org
---
 drivers/staging/zram/zram_sysfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c
index 8cb7822..e239d94 100644
--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -179,8 +179,10 @@ static ssize_t mem_used_total_show(struct device *dev,
 	struct zram *zram = dev_to_zram(dev);
 	struct zram_meta *meta = zram->meta;
 
+	down_read(&zram->init_lock);
 	if (zram->init_done)
 		val = zs_get_total_size_bytes(meta->mem_pool);
+	up_read(&zram->init_lock);
 
 	return sprintf(buf, "%llu\n", val);
 }
-- 
1.8.1.2

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