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    Subject[PATCH 4.9 32/32] loop: remember whether sysfs_create_group() was done
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

    commit d3349b6b3c373ac1fbfb040b810fcee5e2adc7e0 upstream.

    syzbot is hitting WARN() triggered by memory allocation fault
    injection [1] because loop module is calling sysfs_remove_group()
    when sysfs_create_group() failed.
    Fix this by remembering whether sysfs_create_group() succeeded.

    [1] https://syzkaller.appspot.com/bug?id=3f86c0edf75c86d2633aeb9dd69eccc70bc7e90b

    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Reported-by: syzbot <syzbot+9f03168400f56df89dbc6f1751f4458fe739ff29@syzkaller.appspotmail.com>
    Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    Renamed sysfs_ready -> sysfs_inited.

    Signed-off-by: Jens Axboe <axboe@kernel.dk>

    ---
    drivers/block/loop.c | 11 ++++++-----
    drivers/block/loop.h | 1 +
    2 files changed, 7 insertions(+), 5 deletions(-)

    --- a/drivers/block/loop.c
    +++ b/drivers/block/loop.c
    @@ -824,16 +824,17 @@ static struct attribute_group loop_attri
    .attrs= loop_attrs,
    };

    -static int loop_sysfs_init(struct loop_device *lo)
    +static void loop_sysfs_init(struct loop_device *lo)
    {
    - return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
    - &loop_attribute_group);
    + lo->sysfs_inited = !sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
    + &loop_attribute_group);
    }

    static void loop_sysfs_exit(struct loop_device *lo)
    {
    - sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
    - &loop_attribute_group);
    + if (lo->sysfs_inited)
    + sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
    + &loop_attribute_group);
    }

    static void loop_config_discard(struct loop_device *lo)
    --- a/drivers/block/loop.h
    +++ b/drivers/block/loop.h
    @@ -59,6 +59,7 @@ struct loop_device {
    struct kthread_worker worker;
    struct task_struct *worker_task;
    bool use_dio;
    + bool sysfs_inited;

    struct request_queue *lo_queue;
    struct blk_mq_tag_set tag_set;

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