Hi,
在 2023/09/28 16:57, Ming Lei 写道:
> On Thu, Sep 28, 2023 at 04:55:03PM +0800, Yu Kuai wrote:
>> Hi,
>>
>> 在 2023/09/28 15:40, Ming Lei 写道:
>>> On Thu, Sep 28, 2023 at 02:03:28PM +0800, Yu Kuai wrote:
>>>> Hi,
>>>>
>>>> 在 2023/09/28 12:05, Ming Lei 写道:
>>>>> On Mon, Sep 11, 2023 at 10:33:08AM +0800, [email protected] wrote:
>>>>>> From: Li Nan <[email protected]>
>>>>>>
>>>>>> 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.
>>>
>>> OK, got it, thanks for the input.
>>>
>>> But I feel it isn't necessary & fragile to store one extra reference of nsock in
>>> `recv_thread_args`.
>>>
>>> Just run a quick look, the only potential UAF on config->socks should be recv_work(),
>>> so you can retrieve the `nsock` reference at the entry of recv_work(),
>>
>> I don't understand what you mean retrieve the 'nsock', is following what
>> you expected?
>>
>> blk_queue_enter() -> prevent concurrent with nbd_add_socket
>> nsock = config->socks[args->index]
>> blk_queue_exit()
>
> Yeah, turns out you do understand, :-)
Ok, I was not sure about this blk_queue_enter(). By the way, this
remind me of what you did to fix uaf of access queue->mq_hctx[] by
convert the array to xarray.
Maybe it's better to covert config->socks[] to xarray to fix this uaf as
well?
Thanks,
Kuai
On Thu, Sep 28, 2023 at 05:06:40PM +0800, Yu Kuai wrote:
> Hi,
>
> 在 2023/09/28 16:57, Ming Lei 写道:
> > On Thu, Sep 28, 2023 at 04:55:03PM +0800, Yu Kuai wrote:
> > > Hi,
> > >
> > > 在 2023/09/28 15:40, Ming Lei 写道:
> > > > On Thu, Sep 28, 2023 at 02:03:28PM +0800, Yu Kuai wrote:
> > > > > Hi,
> > > > >
> > > > > 在 2023/09/28 12:05, Ming Lei 写道:
> > > > > > On Mon, Sep 11, 2023 at 10:33:08AM +0800, [email protected] wrote:
> > > > > > > From: Li Nan <[email protected]>
> > > > > > >
> > > > > > > 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.
> > > >
> > > > OK, got it, thanks for the input.
> > > >
> > > > But I feel it isn't necessary & fragile to store one extra reference of nsock in
> > > > `recv_thread_args`.
> > > >
> > > > Just run a quick look, the only potential UAF on config->socks should be recv_work(),
> > > > so you can retrieve the `nsock` reference at the entry of recv_work(),
> > >
> > > I don't understand what you mean retrieve the 'nsock', is following what
> > > you expected?
> > >
> > > blk_queue_enter() -> prevent concurrent with nbd_add_socket
> > > nsock = config->socks[args->index]
> > > blk_queue_exit()
> >
> > Yeah, turns out you do understand, :-)
>
> Ok, I was not sure about this blk_queue_enter(). By the way, this
blk_queue_enter() isn't exported, but you can grab ->config_lock
for getting the `nsock`.
> remind me of what you did to fix uaf of access queue->mq_hctx[] by
> convert the array to xarray.
>
>
> Maybe it's better to covert config->socks[] to xarray to fix this uaf as
> well?
->socks[idx] is needed in nbd fast path, so xarray may not be one good idea
since xarray_load() introduces extra load, especially ->socks[] uaf
should exist in recv_work() very likely. For other cases, the active
block request holds queue usage counter.
Thanks,
Ming