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zram: protect sysfs handler from invalid memory access

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commit 5863e10b44 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>
This commit is contained in:
Jiang Liu
2013-06-07 00:07:27 +08:00
committed by Greg Kroah-Hartman
parent 408fd68717
commit c181b46430
1 changed files with 2 additions and 0 deletions
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2
drivers/staging/zram/zram_sysfs.c
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@@ -188,8 +188,10 @@ 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);
}