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From: "Michael Kelley \(LINUX\) via Virtualization" <virtualization@lists.linux-foundation.org>
To: Andrea Parri <parri.andrea@gmail.com>
Cc: Wei Liu <wei.liu@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>,
	Jakub Kicinski <kuba@kernel.org>,
	David Miller <davem@davemloft.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 4/6] hv_sock: Initialize send_buf in hvs_stream_enqueue()
Date: Fri, 15 Apr 2022 14:30:29 +0000	[thread overview]
Message-ID: <PH0PR21MB302526F1483A6FC932AC55CFD7EE9@PH0PR21MB3025.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20220415065041.GC2961@anparri>

From: Andrea Parri <parri.andrea@gmail.com> Sent: Thursday, April 14, 2022 11:51 PM
> 
> > > @@ -655,7 +655,7 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk,
> > > struct msghdr *msg,
> > >
> > >  	BUILD_BUG_ON(sizeof(*send_buf) != HV_HYP_PAGE_SIZE);
> > >
> > > -	send_buf = kmalloc(sizeof(*send_buf), GFP_KERNEL);
> > > +	send_buf = kzalloc(sizeof(*send_buf), GFP_KERNEL);
> >
> > Is this change really needed?
> 
> The idea was...
> 
> 
> > All fields are explicitly initialized, and in the data
> > array, only the populated bytes are copied to the ring buffer.  There should not
> > be any uninitialized values sent to the host.   Zeroing the memory ahead of
> > time certainly provides an extra protection (particularly against padding bytes,
> > but there can't be any since the layout of the data is part of the protocol with
> > Hyper-V).
> 
> Rather than keeping checking that...

The extra protection might be obtained by just zero'ing the header (i.e., the
bytes up to the 16 Kbyte data array).   I don't have a strong preference either
way, so up to you.

Michael

> 
> 
> > It is expensive protection to zero out 16K+ bytes every time we send
> > out a small message.
> 
> Do this.  ;-)
> 
> Will drop the patch.
> 
> Thanks,
>   Andrea
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

WARNING: multiple messages have this Message-ID (diff)
From: "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To: Andrea Parri <parri.andrea@gmail.com>
Cc: KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
	Stefano Garzarella <sgarzare@redhat.com>,
	David Miller <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 4/6] hv_sock: Initialize send_buf in hvs_stream_enqueue()
Date: Fri, 15 Apr 2022 14:30:29 +0000	[thread overview]
Message-ID: <PH0PR21MB302526F1483A6FC932AC55CFD7EE9@PH0PR21MB3025.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20220415065041.GC2961@anparri>

From: Andrea Parri <parri.andrea@gmail.com> Sent: Thursday, April 14, 2022 11:51 PM
> 
> > > @@ -655,7 +655,7 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk,
> > > struct msghdr *msg,
> > >
> > >  	BUILD_BUG_ON(sizeof(*send_buf) != HV_HYP_PAGE_SIZE);
> > >
> > > -	send_buf = kmalloc(sizeof(*send_buf), GFP_KERNEL);
> > > +	send_buf = kzalloc(sizeof(*send_buf), GFP_KERNEL);
> >
> > Is this change really needed?
> 
> The idea was...
> 
> 
> > All fields are explicitly initialized, and in the data
> > array, only the populated bytes are copied to the ring buffer.  There should not
> > be any uninitialized values sent to the host.   Zeroing the memory ahead of
> > time certainly provides an extra protection (particularly against padding bytes,
> > but there can't be any since the layout of the data is part of the protocol with
> > Hyper-V).
> 
> Rather than keeping checking that...

The extra protection might be obtained by just zero'ing the header (i.e., the
bytes up to the 16 Kbyte data array).   I don't have a strong preference either
way, so up to you.

Michael

> 
> 
> > It is expensive protection to zero out 16K+ bytes every time we send
> > out a small message.
> 
> Do this.  ;-)
> 
> Will drop the patch.
> 
> Thanks,
>   Andrea

  reply	other threads:[~2022-04-15 14:30 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-13 20:47 [RFC PATCH 0/6] hv_sock: Hardening changes Andrea Parri (Microsoft)
2022-04-13 20:47 ` [RFC PATCH 1/6] hv_sock: Check hv_pkt_iter_first_raw()'s return value Andrea Parri (Microsoft)
2022-04-15  3:33   ` Michael Kelley (LINUX) via Virtualization
2022-04-15  3:33     ` Michael Kelley (LINUX)
2022-04-15  6:41     ` Andrea Parri
2022-04-15 14:27       ` Michael Kelley (LINUX) via Virtualization
2022-04-15 14:27         ` Michael Kelley (LINUX)
2022-04-15 16:09         ` Andrea Parri
2022-04-13 20:47 ` [RFC PATCH 2/6] hv_sock: Copy packets sent by Hyper-V out of the ring buffer Andrea Parri (Microsoft)
2022-04-15  3:33   ` Michael Kelley (LINUX) via Virtualization
2022-04-15  3:33     ` Michael Kelley (LINUX)
2022-04-15  6:42     ` Andrea Parri
2022-04-13 20:47 ` [RFC PATCH 3/6] hv_sock: Add validation for untrusted Hyper-V values Andrea Parri (Microsoft)
2022-04-13 20:47 ` [RFC PATCH 4/6] hv_sock: Initialize send_buf in hvs_stream_enqueue() Andrea Parri (Microsoft)
2022-04-15  3:33   ` Michael Kelley (LINUX) via Virtualization
2022-04-15  3:33     ` Michael Kelley (LINUX)
2022-04-15  6:50     ` Andrea Parri
2022-04-15 14:30       ` Michael Kelley (LINUX) via Virtualization [this message]
2022-04-15 14:30         ` Michael Kelley (LINUX)
2022-04-15 16:16         ` Andrea Parri
2022-04-13 20:47 ` [RFC PATCH 5/6] Drivers: hv: vmbus: Accept hv_sock offers in isolated guests Andrea Parri (Microsoft)
2022-04-15  3:33   ` Michael Kelley (LINUX) via Virtualization
2022-04-15  3:33     ` Michael Kelley (LINUX)
2022-04-15  6:58     ` Andrea Parri
2022-04-13 20:47 ` [RFC PATCH 6/6] Drivers: hv: vmbus: Refactor the ring-buffer iterator functions Andrea Parri (Microsoft)
2022-04-15  3:34   ` Michael Kelley (LINUX) via Virtualization
2022-04-15  3:34     ` Michael Kelley (LINUX)
2022-04-15  7:00     ` Andrea Parri
2022-04-15 16:28       ` Andrea Parri
2022-04-15 16:44         ` Michael Kelley (LINUX)
2022-04-15 16:44           ` Michael Kelley (LINUX) via Virtualization
2022-04-15 17:05           ` Andrea Parri

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