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    Subject[PATCH 009/145] zram: avoid invalid memory access in zram_exit()
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    3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Jiang Liu <liuj97@gmail.com>

    commit 6030ea9b35971a4200062f010341ab832e878ac9 upstream.

    Memory for zram->disk object may have already been freed after returning
    from destroy_device(zram), then it's unsafe for zram_reset_device(zram)
    to access zram->disk again.

    We can't solve this bug by flipping the order of destroy_device(zram)
    and zram_reset_device(zram), that will cause deadlock issues to the
    zram sysfs handler.

    So fix it by holding an extra reference to zram->disk before calling
    destroy_device(zram).

    Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    [ luis: backported to 3.8: adjusted context ]
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/staging/zram/zram_drv.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
    index 071e058..c9c1e0e 100644
    --- a/drivers/staging/zram/zram_drv.c
    +++ b/drivers/staging/zram/zram_drv.c
    @@ -764,9 +764,11 @@ static void __exit zram_exit(void)
    for (i = 0; i < num_devices; i++) {
    zram = &zram_devices[i];

    + get_disk(zram->disk);
    destroy_device(zram);
    if (zram->init_done)
    zram_reset_device(zram);
    + put_disk(zram->disk);
    }

    unregister_blkdev(zram_major, "zram");
    --
    1.8.1.2


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