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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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