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Message-ID: <47669fb6-3700-e327-11af-93a92b0984a0@huaweicloud.com>
Date: Thu, 28 Sep 2023 14:03:28 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Ming Lei <ming.lei@...hat.com>, linan666@...weicloud.com
Cc: josef@...icpanda.com, axboe@...nel.dk, linux-block@...r.kernel.org,
nbd@...er.debian.org, linux-kernel@...r.kernel.org,
linan122@...wei.com, yi.zhang@...wei.com, houtao1@...wei.com,
yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] nbd: pass nbd_sock to nbd_read_reply() instead of index
Hi,
在 2023/09/28 12:05, Ming Lei 写道:
> On Mon, Sep 11, 2023 at 10:33:08AM +0800, linan666@...weicloud.com wrote:
>> From: Li Nan <linan122@...wei.com>
>>
>> If a socket is processing ioctl 'NBD_SET_SOCK', config->socks might be
>> krealloc in nbd_add_socket(), and a garbage request is received now, a UAF
>> may occurs.
>>
>> T1
>> nbd_ioctl
>> __nbd_ioctl
>> nbd_add_socket
>> blk_mq_freeze_queue
>> T2
>> recv_work
>> nbd_read_reply
>> sock_xmit
>> krealloc config->socks
>> def config->socks
>>
>> Pass nbd_sock to nbd_read_reply(). And introduce a new function
>> sock_xmit_recv(), which differs from sock_xmit only in the way it get
>> socket.
>>
>
> I am wondering why not grab queue usage counter before calling nbd_read_reply()
> for avoiding such issue, something like the following change:
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index df1cd0f718b8..09215b605b12 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -837,9 +837,6 @@ static void recv_work(struct work_struct *work)
> while (1) {
> struct nbd_reply reply;
>
> - if (nbd_read_reply(nbd, args->index, &reply))
> - break;
> -
> /*
> * Grab .q_usage_counter so request pool won't go away, then no
> * request use-after-free is possible during nbd_handle_reply().
> @@ -852,6 +849,9 @@ static void recv_work(struct work_struct *work)
> break;
> }
>
This break how nbd works, if there is no reply yet, recv_work() will
wait for reply in:
nbd_read_reply
sock_xmit
sock_recvmsg
After this change, recv_work() will just return if there is no io.
Thanks,
Kuai
> + if (nbd_read_reply(nbd, args->index, &reply))
> + break;
> +
> cmd = nbd_handle_reply(nbd, args->index, &reply);
> if (IS_ERR(cmd)) {
> percpu_ref_put(&q->q_usage_counter);
>
> Thanks,
> Ming
>
> .
>
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