Re: [PATCH] rbd: avoid use-after-free in do_rbd_add() when rbd_dev_create() fails

[Ilya Dryomov]

On Sun, Feb 26, 2023 at 8:52 PM Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>
> If getting an ID or setting up a work queue in rbd_dev_create() fails,
> use-after-free on rbd_dev->rbd_client, rbd_dev->spec and rbd_dev->opts
> is triggered in do_rbd_add().  The root cause is that the ownership of
> these structures is transfered to rbd_dev prematurely and they all end
> up getting freed when rbd_dev_create() calls rbd_dev_free() prior to
> returning to do_rbd_add().
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE, an
> incomplete patch submitted by Natalia Petrova <n.petrova@xxxxxxxxxx>.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 1643dfa4c2c8 ("rbd: introduce a per-device ordered workqueue")
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
> ---
>  drivers/block/rbd.c | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 04453f4a319c..60aed196a2e5 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -5292,8 +5292,7 @@ static void rbd_dev_release(struct device *dev)
>                 module_put(THIS_MODULE);
>  }
>
> -static struct rbd_device *__rbd_dev_create(struct rbd_client *rbdc,
> -                                          struct rbd_spec *spec)
> +static struct rbd_device *__rbd_dev_create(struct rbd_spec *spec)
>  {
>         struct rbd_device *rbd_dev;
>
> @@ -5338,9 +5337,6 @@ static struct rbd_device *__rbd_dev_create(struct rbd_client *rbdc,
>         rbd_dev->dev.parent = &rbd_root_dev;
>         device_initialize(&rbd_dev->dev);
>
> -       rbd_dev->rbd_client = rbdc;
> -       rbd_dev->spec = spec;
> -
>         return rbd_dev;
>  }
>
> @@ -5353,12 +5349,10 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
>  {
>         struct rbd_device *rbd_dev;
>
> -       rbd_dev = __rbd_dev_create(rbdc, spec);
> +       rbd_dev = __rbd_dev_create(spec);
>         if (!rbd_dev)
>                 return NULL;
>
> -       rbd_dev->opts = opts;
> -
>         /* get an id and fill in device name */
>         rbd_dev->dev_id = ida_simple_get(&rbd_dev_id_ida, 0,
>                                          minor_to_rbd_dev_id(1 << MINORBITS),
> @@ -5375,6 +5369,10 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
>         /* we have a ref from do_rbd_add() */
>         __module_get(THIS_MODULE);
>
> +       rbd_dev->rbd_client = rbdc;
> +       rbd_dev->spec = spec;
> +       rbd_dev->opts = opts;
> +
>         dout("%s rbd_dev %p dev_id %d\n", __func__, rbd_dev, rbd_dev->dev_id);
>         return rbd_dev;
>
> @@ -6736,7 +6734,7 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev, int depth)
>                 goto out_err;
>         }
>
> -       parent = __rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec);
> +       parent = __rbd_dev_create(rbd_dev->parent_spec);
>         if (!parent) {
>                 ret = -ENOMEM;
>                 goto out_err;
> @@ -6746,8 +6744,8 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev, int depth)
>          * Images related by parent/child relationships always share
>          * rbd_client and spec/parent_spec, so bump their refcounts.
>          */
> -       __rbd_get_client(rbd_dev->rbd_client);
> -       rbd_spec_get(rbd_dev->parent_spec);
> +       parent->rbd_client = __rbd_get_client(rbd_dev->rbd_client);
> +       parent->spec = rbd_spec_get(rbd_dev->parent_spec);
>
>         __set_bit(RBD_DEV_FLAG_READONLY, &parent->flags);
>
> --
> 2.39.1
>

CCing everyone on the previous thread...