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Subject[PATCH 013/145] zram: protect sysfs handler from invalid memory access
Date
3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jiang Liu <liuj97@gmail.com>

commit 5863e10b441e7ea4b492f930f1be180a97d026f3 upstream.

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@huawei.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ luis: backported to 3.8:
- protect access to zram->mem_pool instead of zram->meta ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
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 de1eacf..c07687e 100644
--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -186,8 +186,10 @@ static ssize_t mem_used_total_show(struct device *dev,
u64 val = 0;
struct zram *zram = dev_to_zram(dev);

+ down_read(&zram->init_lock);
if (zram->init_done)
val = zs_get_total_size_bytes(zram->mem_pool);
+ up_read(&zram->init_lock);

return sprintf(buf, "%llu\n", val);
}
--
1.8.1.2


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