From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: 163 <freedomsky1986@163.com>, linux-hyperv@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Wei Liu <wei.liu@kernel.org>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
Michael Kelley <mikelley@microsoft.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"Andrea Parri \(Microsoft\)" <parri.andrea@gmail.com>
Subject: Re: [EXTERNAL] [PATCH 1/5] Drivers: hv: copy from message page only what's needed
Date: Thu, 02 Apr 2020 18:26:52 +0200 [thread overview]
Message-ID: <87a73tzwdv.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <3ed15a02-0b86-0ec1-6daf-df94f8fc6ba5@163.com>
163 <freedomsky1986@163.com> writes:
> On 4/1/2020 6:36 PM, Vitaly Kuznetsov wrote:
>> Hyper-V Interrupt Message Page (SIMP) has 16 256-byte slots for
>> messages. Each message comes with a header (16 bytes) which specifies the
>> payload length (up to 240 bytes). vmbus_on_msg_dpc(), however, doesn't
>> look at the real message length and copies the whole slot to a temporary
>> buffer before passing it to message handlers. This is potentially dangerous
>> as hypervisor doesn't have to clean the whole slot when putting a new
>> message there and a message handler can get access to some data which
>> belongs to a previous message.
>>
>> Note, this is not currently a problem because all message handlers are
>> in-kernel but eventually we may e.g. get this exported to userspace.
>>
>> Note also, that this is not a performance critical path: messages (unlike
>> events) represent rare events so it doesn't really matter (from performance
>> point of view) if we copy too much.
>>
>> Fix the issue by taking into account the real message length. The temporary
>> buffer allocated by vmbus_on_msg_dpc() remains fixed size for now.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> drivers/hv/vmbus_drv.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
>> index 029378c27421..2b5572146358 100644
>> --- a/drivers/hv/vmbus_drv.c
>> +++ b/drivers/hv/vmbus_drv.c
>> @@ -1043,7 +1043,8 @@ void vmbus_on_msg_dpc(unsigned long data)
>> return;
>>
>> INIT_WORK(&ctx->work, vmbus_onmessage_work);
>> - memcpy(&ctx->msg, msg, sizeof(*msg));
>> + memcpy(&ctx->msg, msg, sizeof(msg->header) +
>> + msg->header.payload_size);
>>
>
> Hi Vitaly:
> I think we still need to check whether the payload_size passed from
> Hyper-V is valid or not here to avoid cross-border issue before doing
> copying.
Sure,
the header.payload_size must be 0 <= header.payload_size <= 240
I'll add the check.
--
Vitaly
next prev parent reply other threads:[~2020-04-02 16:27 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-01 10:36 [PATCH 0/5] Drivers: hv: cleanup VMBus messages handling Vitaly Kuznetsov
2020-04-01 10:36 ` [PATCH 1/5] Drivers: hv: copy from message page only what's needed Vitaly Kuznetsov
2020-04-02 14:46 ` [EXTERNAL] " 163
2020-04-02 16:26 ` Vitaly Kuznetsov [this message]
2020-04-03 1:52 ` Michael Kelley
2020-04-03 7:03 ` Vitaly Kuznetsov
2020-04-01 10:36 ` [PATCH 2/5] Drivers: hv: allocate the exact needed memory for messages Vitaly Kuznetsov
2020-04-03 1:54 ` Michael Kelley
2020-04-01 10:36 ` [PATCH 3/5] Drivers: hv: avoid passing opaque pointer to vmbus_onmessage() Vitaly Kuznetsov
2020-04-03 1:55 ` Michael Kelley
2020-04-01 10:38 ` [PATCH 4/5] Drivers: hv: make sure that 'struct vmbus_channel_message_header' compiles correctly Vitaly Kuznetsov
2020-04-01 10:38 ` [PATCH 5/5] Drivers: hv: check VMBus messages lengths Vitaly Kuznetsov
2020-04-03 2:00 ` Michael Kelley
2020-04-03 7:07 ` Vitaly Kuznetsov
2020-04-03 1:56 ` [PATCH 4/5] Drivers: hv: make sure that 'struct vmbus_channel_message_header' compiles correctly Michael Kelley
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