From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Ilya Maximets <i.maximets@samsung.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Xie, Huawei" <huawei.xie@intel.com>,
Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Dyasly Sergey <s.dyasly@samsung.com>,
Heetae Ahn <heetae82.ahn@samsung.com>
Subject: Re: [dpdk-dev] [PATCH] vhost: fix segfault on bad descriptor address.
Date: Tue, 31 May 2016 14:53:03 +0800 [thread overview]
Message-ID: <1bb65424-fda0-8e60-554d-66ccc19e7d90@intel.com> (raw)
In-Reply-To: <574C3107.1070305@samsung.com>
Hi,
On 5/30/2016 8:24 PM, Ilya Maximets wrote:
> On 30.05.2016 15:00, Tan, Jianfeng wrote:
>> Hi,
>>
>>> -----Original Message-----
>>> From: Ilya Maximets [mailto:i.maximets@samsung.com]
>>> Sent: Friday, May 20, 2016 8:50 PM
>>> To: dev@dpdk.org; Xie, Huawei; Yuanhan Liu
>>> Cc: Dyasly Sergey; Heetae Ahn; Tan, Jianfeng; Ilya Maximets
>>> Subject: [PATCH] vhost: fix segfault on bad descriptor address.
>>>
>>> In current implementation guest application can reinitialize vrings
>>> by executing start after stop. In the same time host application
>>> can still poll virtqueue while device stopped in guest and it will
>>> crash with segmentation fault while vring reinitialization because
>>> of dereferencing of bad descriptor addresses.
>>>
>>> OVS crash for example:
>>> <------------------------------------------------------------------------>
>>> [test-pmd inside guest VM]
>>>
>>> testpmd> port stop all
>>> Stopping ports...
>>> Checking link statuses...
>>> Port 0 Link Up - speed 10000 Mbps - full-duplex
>>> Done
>>> testpmd> port config all rxq 2
>>> testpmd> port config all txq 2
>>> testpmd> port start all
>>> Configuring Port 0 (socket 0)
>>> Port 0: 52:54:00:CB:44:C8
>>> Checking link statuses...
>>> Port 0 Link Up - speed 10000 Mbps - full-duplex
>>> Done
>>>
>>> [OVS on host]
>>> Program received signal SIGSEGV, Segmentation fault.
>>> rte_memcpy (n=2056, src=0xc, dst=0x7ff4d5247000) at
>>> rte_memcpy.h
>>>
>>> (gdb) bt
>>> #0 rte_memcpy (n=2056, src=0xc, dst=0x7ff4d5247000)
>>> #1 copy_desc_to_mbuf
>>> #2 rte_vhost_dequeue_burst
>>> #3 netdev_dpdk_vhost_rxq_recv
>>> ...
>>>
>>> (gdb) bt full
>>> #0 rte_memcpy
>>> ...
>>> #1 copy_desc_to_mbuf
>>> desc_addr = 0
>>> mbuf_offset = 0
>>> desc_offset = 12
>>> ...
>>> <------------------------------------------------------------------------>
>>>
>>> Fix that by checking addresses of descriptors before using them.
>>>
>>> Note: For mergeable buffers this patch checks only guest's address for
>>> zero, but in non-meargeable case host's address checked. This is done
>>> because checking of host's address in mergeable case requires additional
>>> refactoring to keep virtqueue in consistent state in case of error.
>>
>> I agree with you that it should be fixed because malicious guest could launch
>> DOS attack on vswitch with the current implementation.
>>
>> But I don't understand why you do not fix the mergable case in
>> copy_mbuf_to_desc_mergable() on where gpa_to_vva() happens? And the change in
>> fill_vec_buf(), checking !vq->desc[idx].addr, make any sense?
>>
>> Thanks,
>> Jianfeng
> Hi.
> As I said inside commit-message, checking of host's address in mergeable case
> requires additional refactoring to keep virtqueue in consistent state.
>
> There are few issues with checking inside copy_mbuf_to_desc_mergable() :
>
> 1. Ring elements already reserved and we must fill them with some
> sane data before going out of virtio_dev_merge_rx().
>
> 2. copy_mbuf_to_desc_mergable() can't return an error in current
> implementation (additional checking needed), otherwise used->idx
> will be decremented (I think, it's bad).
Yes, currently there is no way to return these invalid desc back to
virtio because there's no invalid flag in virtio_net_hdr to indicate
this desc contains no pkt. I see kernel just skips those descriptors
with bad addr. I think it may rely on reset of the virtio device to
improve such situation.
Another thing is that, your patch only checks the desc->addr, but we
should check desc->addr + desc->len too, right?
Thanks,
Jianfeng
>
>
> Checking !vq->desc[idx].addr inside fill_vec_buf() make sense in case of virtio
> reinitialization, because guest's address will be zero (case described in
> commit-message). Checking of guest's address will not help in case of bad and
> not NULL address, but useful in this common case.
> Also, we can't catch bad address what we able to map, so, malicious guest could
> break vhost anyway.
>
> I agree, that checking of host's address is better, but this may be done later
> together with resolving above issues.
>
> Best regards, Ilya Maximets.
next prev parent reply other threads:[~2016-05-31 6:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-20 12:50 Ilya Maximets
2016-05-23 10:57 ` Yuanhan Liu
2016-05-23 11:04 ` Ilya Maximets
2016-05-30 11:05 ` Ilya Maximets
2016-05-30 14:25 ` Yuanhan Liu
2016-05-31 9:12 ` Ilya Maximets
2016-05-30 12:00 ` Tan, Jianfeng
2016-05-30 12:24 ` Ilya Maximets
2016-05-31 6:53 ` Tan, Jianfeng [this message]
2016-05-31 9:10 ` Ilya Maximets
2016-05-31 22:06 ` Rich Lane
2016-06-02 10:46 ` Ilya Maximets
2016-06-02 16:22 ` Rich Lane
2016-06-03 6:01 ` Ilya Maximets
2016-07-01 7:35 ` Yuanhan Liu
2016-07-06 11:19 ` Ilya Maximets
2016-07-06 12:24 ` Yuanhan Liu
2016-07-08 11:48 ` Ilya Maximets
2016-07-10 13:17 ` Yuanhan Liu
2016-07-11 8:38 ` Yuanhan Liu
2016-07-11 9:50 ` Ilya Maximets
2016-07-11 11:05 ` Yuanhan Liu
2016-07-11 11:47 ` Ilya Maximets
2016-07-12 2:43 ` Yuanhan Liu
2016-07-12 5:53 ` Ilya Maximets
2016-07-13 7:34 ` Ilya Maximets
2016-07-13 8:47 ` Yuanhan Liu
2016-07-13 15:54 ` Rich Lane
2016-07-14 1:42 ` Yuanhan Liu
2016-07-14 4:38 ` Ilya Maximets
2016-07-14 8:18 ` [dpdk-dev] [PATCH v2] " Ilya Maximets
2016-07-15 6:17 ` Yuanhan Liu
2016-07-15 7:23 ` Ilya Maximets
2016-07-15 8:40 ` Yuanhan Liu
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 0/2] " Ilya Maximets
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 1/2] vhost: fix using of bad return value on mergeable enqueue Ilya Maximets
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 2/2] vhost: do sanity check for ring descriptor address Ilya Maximets
2016-07-15 12:14 ` [dpdk-dev] [PATCH v3 0/2] vhost: fix segfault on bad " Yuanhan Liu
2016-07-15 19:37 ` Thomas Monjalon
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