linux-kernel - Re: [PATCH] rbd: avoid double free memory on error path in rbd_dev

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Message-ID: <CAOi1vP_7Oaw8O-p2X1xymzym1Xf_RZeN0u=SeE4Zbc2y+AfgYA@mail.gmail.com>
Date:   Mon, 6 Feb 2023 12:58:33 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Natalia Petrova <n.petrova@...tech.ru>
Cc:     Dongsheng Yang <dongsheng.yang@...ystack.cn>,
        Jens Axboe <axboe@...nel.dk>, ceph-devel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: Re: [PATCH] rbd: avoid double free memory on error path in rbd_dev_create()

On Fri, Feb 3, 2023 at 3:15 PM Natalia Petrova <n.petrova@...tech.ru> wrote:
>
> If rbd_dev_create() fails after assignment 'opts' to 'rbd_dev->opts',
> double free of 'rbd_options' happens:
> one is in rbd_dev_free() and another one is in do_rbd_add().
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 1643dfa4c2c8 ("rbd: introduce a per-device ordered workqueue")
> Signed-off-by: Natalia Petrova <n.petrova@...tech.ru>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
> ---
>  drivers/block/rbd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 04453f4a319c..ab6bfc352cde 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -5357,7 +5357,6 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
>         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,
> @@ -5372,6 +5371,7 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
>         if (!rbd_dev->task_wq)
>                 goto fail_dev_id;
>
> +       rbd_dev->opts = opts;
>         /* we have a ref from do_rbd_add() */
>         __module_get(THIS_MODULE);
>
> --
> 2.34.1
>

Hi Natalia,

It seems like a similar issue is affecting rbd_dev->rbd_client and
rbd_dev->spec.  Unlike rbd_dev->opts, they are ref-counted and I'm
guessing that the verification tool doesn't go that deep.

I'd prefer all three to be addressed in the same change, since it's the
same error path.  Would you be willing to look into that and post a new
revision or should I treat just this patch as a bug report?

Thanks,

                Ilya