Re: [PATCH 3/3] scsi: storvsc: Validate length of incoming packet in storvsc_on_channel_callback()

From: Andrea Parri <parri.andrea@gmail.com>
To: Olaf Hering <olaf@aepfle.de>
Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org,
	"K . Y . 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>,
	Michael Kelley <mikelley@microsoft.com>,
	Saruhan Karademir <skarade@microsoft.com>,
	Juan Vazquez <juvazq@microsoft.com>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org
Subject: Re: [PATCH 3/3] scsi: storvsc: Validate length of incoming packet in storvsc_on_channel_callback()
Date: Tue, 30 Mar 2021 11:08:15 +0200	[thread overview]
Message-ID: <20210330090815.GA1897@anparri> (raw)
In-Reply-To: <YGICQc6HaYw8+uES@aepfle.de>

Hi Olaf,

On Mon, Mar 29, 2021 at 06:37:21PM +0200, Olaf Hering wrote:
> On Thu, Dec 17, Andrea Parri (Microsoft) wrote:
> 
> > Check that the packet is of the expected size at least, don't copy data
> > past the packet.
> 
> > +		if (hv_pkt_datalen(desc) < sizeof(struct vstor_packet) -
> > +				stor_device->vmscsi_size_delta) {
> > +			dev_err(&device->device, "Invalid packet len\n");
> > +			continue;
> > +		}
> > +
> 
> Sorry for being late:
> 
> It might be just cosmetic, but should this check be done prior the call to vmbus_request_addr()?

TBH, I'm not immediately seeing why it 'should'; it could make sense to move
the check on the packet data length.

> Unrelated: my copy of vmbus_request_addr() can return 0, which is apparently not handled by this loop in storvsc_on_channel_callback().

Indeed, IDs of 0 are reserved for so called unsolicited messages; I think we
should check that storvsc_on_io_completion() is not called on such messages.

Thanks,
  Andrea