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    Subject[PATCH 5.6 017/166] rbd: call rbd_dev_unprobe() after unwatching and flushing notifies
    Date
    From: Ilya Dryomov <idryomov@gmail.com>

    commit 952c48b0ed18919bff7528501e9a3fff8a24f8cd upstream.

    rbd_dev_unprobe() is supposed to undo most of rbd_dev_image_probe(),
    including rbd_dev_header_info(), which means that rbd_dev_header_info()
    isn't supposed to be called after rbd_dev_unprobe().

    However, rbd_dev_image_release() calls rbd_dev_unprobe() before
    rbd_unregister_watch(). This is racy because a header update notify
    can sneak in:

    "rbd unmap" thread ceph-watch-notify worker

    rbd_dev_image_release()
    rbd_dev_unprobe()
    free and zero out header
    rbd_watch_cb()
    rbd_dev_refresh()
    rbd_dev_header_info()
    read in header

    The same goes for "rbd map" because rbd_dev_image_probe() calls
    rbd_dev_unprobe() on errors. In both cases this results in a memory
    leak.

    Fixes: fd22aef8b47c ("rbd: move rbd_unregister_watch() call into rbd_dev_image_release()")
    Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
    Reviewed-by: Jason Dillaman <dillaman@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/block/rbd.c | 8 ++++----
    1 file changed, 4 insertions(+), 4 deletions(-)

    --- a/drivers/block/rbd.c
    +++ b/drivers/block/rbd.c
    @@ -6955,9 +6955,10 @@ static void rbd_print_dne(struct rbd_dev

    static void rbd_dev_image_release(struct rbd_device *rbd_dev)
    {
    - rbd_dev_unprobe(rbd_dev);
    if (rbd_dev->opts)
    rbd_unregister_watch(rbd_dev);
    +
    + rbd_dev_unprobe(rbd_dev);
    rbd_dev->image_format = 0;
    kfree(rbd_dev->spec->image_id);
    rbd_dev->spec->image_id = NULL;
    @@ -7007,7 +7008,7 @@ static int rbd_dev_image_probe(struct rb
    if (ret) {
    if (ret == -ENOENT && !need_watch)
    rbd_print_dne(rbd_dev, false);
    - goto err_out_watch;
    + goto err_out_probe;
    }

    /*
    @@ -7052,12 +7053,11 @@ static int rbd_dev_image_probe(struct rb
    return 0;

    err_out_probe:
    - rbd_dev_unprobe(rbd_dev);
    -err_out_watch:
    if (!depth)
    up_write(&rbd_dev->header_rwsem);
    if (need_watch)
    rbd_unregister_watch(rbd_dev);
    + rbd_dev_unprobe(rbd_dev);
    err_out_format:
    rbd_dev->image_format = 0;
    kfree(rbd_dev->spec->image_id);

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