[ 065/102] zram: protect sysfs handler from invalid memory access

From: Greg Kroah-Hartman
Date: Thu Aug 08 2013 - 22:09:58 EST

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


From: Jiang Liu <liuj97@xxxxxxxxx>

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

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@xxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/staging/zram/zram_sysfs.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -188,8 +188,10 @@ static ssize_t mem_used_total_show(struc
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);

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