From: Mike Christie <mchristi@redhat.com>
To: Sun Ke <sunke32@huawei.com>, josef@toxicpanda.com, axboe@kernel.dk
Cc: linux-block@vger.kernel.org, nbd@other.debian.org,
linux-kernel@vger.kernel.org
Subject: Re: [v3] nbd: fix potential NULL pointer fault in nbd_genl_disconnect
Date: Mon, 10 Feb 2020 11:05:38 -0600 [thread overview]
Message-ID: <5E418D62.8090102@redhat.com> (raw)
In-Reply-To: <20200210073241.41813-1-sunke32@huawei.com>
On 02/10/2020 01:32 AM, Sun Ke wrote:
> Open /dev/nbdX first, the config_refs will be 1 and
> the pointers in nbd_device are still null. Disconnect
> /dev/nbdX, then reference a null recv_workq. The
> protection by config_refs in nbd_genl_disconnect is useless.
>
> To fix it, just add a check for a non null task_recv in
> nbd_genl_disconnect.
>
> Signed-off-by: Sun Ke <sunke32@huawei.com>
> ---
> v1 -> v2:
> Add an omitted mutex_unlock.
>
> v2 -> v3:
> Add nbd->config_lock, suggested by Josef.
> ---
> drivers/block/nbd.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index b4607dd96185..870b3fd0c101 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -2008,12 +2008,20 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
> index);
> return -EINVAL;
> }
> + mutex_lock(&nbd->config_lock);
> if (!refcount_inc_not_zero(&nbd->refs)) {
> + mutex_unlock(&nbd->config_lock);
> mutex_unlock(&nbd_index_mutex);
> printk(KERN_ERR "nbd: device at index %d is going down\n",
> index);
> return -EINVAL;
> }
> + if (!nbd->recv_workq) {
> + mutex_unlock(&nbd->config_lock);
> + mutex_unlock(&nbd_index_mutex);
> + return -EINVAL;
> + }
> + mutex_unlock(&nbd->config_lock);
> mutex_unlock(&nbd_index_mutex);
> if (!refcount_inc_not_zero(&nbd->config_refs)) {
> nbd_put(nbd);
>
With my other patch then we will not need this right? It handles your
case by just being integrated with the existing checks in:
nbd_disconnect_and_put->nbd_clear_sock->sock_shutdown
...
static void sock_shutdown(struct nbd_device *nbd)
{
....
if (config->num_connections == 0)
return;
num_connections is zero for your case since we never did a
nbd_genl_disconnect so we would return here.
next prev parent reply other threads:[~2020-02-10 17:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 7:32 [v3] nbd: fix potential NULL pointer fault in nbd_genl_disconnect Sun Ke
2020-02-10 17:05 ` Mike Christie [this message]
2020-02-11 4:12 ` sunke (E)
2020-02-11 16:39 ` Mike Christie
2020-02-12 2:00 ` sunke (E)
2020-06-01 11:41 ` Sun Ke
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