Re: [PATCH v4 2/3] scsi: storvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening

[Wei Liu <wei.liu@kernel.org>]

On Tue, Jul 07, 2020 at 04:47:00PM -0700, Nathan Chancellor wrote:
> Hi Andres,
> 
> On Tue, Jun 30, 2020 at 08:12:20PM -0400, Andres Beltran wrote:
> > Currently, pointers to guest memory are passed to Hyper-V as
> > transaction IDs in storvsc. In the face of errors or malicious
> > behavior in Hyper-V, storvsc should not expose or trust the transaction
> > IDs returned by Hyper-V to be valid guest memory addresses. Instead,
> > use small integers generated by vmbus_requestor as requests
> > (transaction) IDs.
> > 
> > Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
> > Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> > Cc: linux-scsi@vger.kernel.org
> > Signed-off-by: Andres Beltran <lkmlabelt@gmail.com>
> > Reviewed-by: Michael Kelley <mikelley@microsoft.com>
> > ---
> > Changes in v2:
> >         - Add casts to unsigned long to fix warnings on 32bit.
> > 
> >  drivers/scsi/storvsc_drv.c | 85 +++++++++++++++++++++++++++++++++-----
> >  1 file changed, 74 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > index 624467e2590a..6d2df1f0fe6d 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -399,6 +399,7 @@ static int storvsc_timeout = 180;
> >  static struct scsi_transport_template *fc_transport_template;
> >  #endif
> >  
> > +static struct scsi_host_template scsi_driver;
> >  static void storvsc_on_channel_callback(void *context);
> >  
> >  #define STORVSC_MAX_LUNS_PER_TARGET			255
> > @@ -698,6 +699,12 @@ static void handle_sc_creation(struct vmbus_channel *new_sc)
> >  
> >  	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
> >  
> > +	/*
> > +	 * The size of vmbus_requestor is an upper bound on the number of requests
> > +	 * that can be in-progress at any one time across all channels.
> > +	 */
> > +	new_sc->rqstor_size = scsi_driver.can_queue;
> > +
> >  	ret = vmbus_open(new_sc,
> >  			 storvsc_ringbuffer_size,
> >  			 storvsc_ringbuffer_size,
> > @@ -726,6 +733,7 @@ static void  handle_multichannel_storage(struct hv_device *device, int max_chns)
> >  	struct storvsc_cmd_request *request;
> >  	struct vstor_packet *vstor_packet;
> >  	int ret, t;
> > +	u64 rqst_id;
> >  
> >  	/*
> >  	 * If the number of CPUs is artificially restricted, such as
> > @@ -760,14 +768,23 @@ static void  handle_multichannel_storage(struct hv_device *device, int max_chns)
> >  	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
> >  	vstor_packet->sub_channel_count = num_sc;
> >  
> > +	rqst_id = vmbus_next_request_id(&device->channel->requestor,
> > +					(unsigned long)request);
> > +	if (rqst_id == VMBUS_RQST_ERROR) {
> > +		dev_err(dev, "No request id available\n");
> > +		return;
> > +	}
> > +
> >  	ret = vmbus_sendpacket(device->channel, vstor_packet,
> >  			       (sizeof(struct vstor_packet) -
> >  			       vmscsi_size_delta),
> > -			       (unsigned long)request,
> > +			       rqst_id,
> >  			       VM_PKT_DATA_INBAND,
> >  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> >  
> >  	if (ret != 0) {
> > +		/* Reclaim request ID to avoid leak of IDs */
> > +		vmbus_request_addr(&device->channel->requestor, rqst_id);
> >  		dev_err(dev, "Failed to create sub-channel: err=%d\n", ret);
> >  		return;
> >  	}
> > @@ -818,20 +835,31 @@ static int storvsc_execute_vstor_op(struct hv_device *device,
> >  {
> >  	struct vstor_packet *vstor_packet;
> >  	int ret, t;
> > +	u64 rqst_id;
> >  
> >  	vstor_packet = &request->vstor_packet;
> >  
> >  	init_completion(&request->wait_event);
> >  	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
> >  
> > +	rqst_id = vmbus_next_request_id(&device->channel->requestor,
> > +					(unsigned long)request);
> > +	if (rqst_id == VMBUS_RQST_ERROR) {
> > +		dev_err(&device->device, "No request id available\n");
> > +		return -EAGAIN;
> > +	}
> > +
> >  	ret = vmbus_sendpacket(device->channel, vstor_packet,
> >  			       (sizeof(struct vstor_packet) -
> >  			       vmscsi_size_delta),
> > -			       (unsigned long)request,
> > +			       rqst_id,
> >  			       VM_PKT_DATA_INBAND,
> >  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> > -	if (ret != 0)
> > +	if (ret != 0) {
> > +		/* Reclaim request ID to avoid leak of IDs */
> > +		vmbus_request_addr(&device->channel->requestor, rqst_id);
> >  		return ret;
> > +	}
> >  
> >  	t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
> >  	if (t == 0)
> > @@ -1233,9 +1261,17 @@ static void storvsc_on_channel_callback(void *context)
> >  	foreach_vmbus_pkt(desc, channel) {
> >  		void *packet = hv_pkt_data(desc);
> >  		struct storvsc_cmd_request *request;
> > +		u64 cmd_rqst;
> >  
> > -		request = (struct storvsc_cmd_request *)
> > -			((unsigned long)desc->trans_id);
> > +		cmd_rqst = vmbus_request_addr(&channel->requestor,
> > +					      desc->trans_id);
> > +		if (cmd_rqst == VMBUS_RQST_ERROR) {
> > +			dev_err(&device->device,
> > +				"Incorrect transaction id\n");
> > +			continue;
> > +		}
> > +
> > +		request = (struct storvsc_cmd_request *)(unsigned long)cmd_rqst;
> >  
> >  		if (request == &stor_device->init_request ||
> >  		    request == &stor_device->reset_request) {
> > @@ -1256,6 +1292,12 @@ static int storvsc_connect_to_vsp(struct hv_device *device, u32 ring_size,
> >  
> >  	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
> >  
> > +	/*
> > +	 * The size of vmbus_requestor is an upper bound on the number of requests
> > +	 * that can be in-progress at any one time across all channels.
> > +	 */
> > +	device->channel->rqstor_size = scsi_driver.can_queue;
> > +
> >  	ret = vmbus_open(device->channel,
> >  			 ring_size,
> >  			 ring_size,
> > @@ -1369,6 +1411,7 @@ static int storvsc_do_io(struct hv_device *device,
> >  	int ret = 0;
> >  	const struct cpumask *node_mask;
> >  	int tgt_cpu;
> > +	u64 rqst_id;
> >  
> >  	vstor_packet = &request->vstor_packet;
> >  	stor_device = get_out_stor_device(device);
> > @@ -1463,6 +1506,13 @@ static int storvsc_do_io(struct hv_device *device,
> >  
> >  	vstor_packet->operation = VSTOR_OPERATION_EXECUTE_SRB;
> >  
> > +	rqst_id = vmbus_next_request_id(&outgoing_channel->requestor,
> > +					(unsigned long)request);
> > +	if (rqst_id == VMBUS_RQST_ERROR) {
> > +		dev_err(&device->device, "No request id available\n");
> > +		return -EAGAIN;
> > +	}
> > +
> >  	if (request->payload->range.len) {
> >  
> >  		ret = vmbus_sendpacket_mpb_desc(outgoing_channel,
> > @@ -1470,18 +1520,21 @@ static int storvsc_do_io(struct hv_device *device,
> >  				vstor_packet,
> >  				(sizeof(struct vstor_packet) -
> >  				vmscsi_size_delta),
> > -				(unsigned long)request);
> > +				rqst_id);
> >  	} else {
> >  		ret = vmbus_sendpacket(outgoing_channel, vstor_packet,
> >  			       (sizeof(struct vstor_packet) -
> >  				vmscsi_size_delta),
> > -			       (unsigned long)request,
> > +			       rqst_id,
> >  			       VM_PKT_DATA_INBAND,
> >  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> >  	}
> >  
> > -	if (ret != 0)
> > +	if (ret != 0) {
> > +		/* Reclaim request ID to avoid leak of IDs */
> > +		vmbus_request_addr(&outgoing_channel->requestor, rqst_id);
> >  		return ret;
> > +	}
> >  
> >  	atomic_inc(&stor_device->num_outstanding_req);
> >  
> > @@ -1562,7 +1615,7 @@ static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
> >  	struct storvsc_cmd_request *request;
> >  	struct vstor_packet *vstor_packet;
> >  	int ret, t;
> > -
> > +	u64 rqst_id;
> >  
> >  	stor_device = get_out_stor_device(device);
> >  	if (!stor_device)
> > @@ -1577,14 +1630,24 @@ static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
> >  	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
> >  	vstor_packet->vm_srb.path_id = stor_device->path_id;
> >  
> > +	rqst_id = vmbus_next_request_id(&device->channel->requestor,
> > +					(unsigned long)&stor_device->reset_request);
> > +	if (rqst_id == VMBUS_RQST_ERROR) {
> > +		dev_err(&device->device, "No request id available\n");
> > +		return FAILED;
> > +	}
> > +
> >  	ret = vmbus_sendpacket(device->channel, vstor_packet,
> >  			       (sizeof(struct vstor_packet) -
> >  				vmscsi_size_delta),
> > -			       (unsigned long)&stor_device->reset_request,
> > +			       rqst_id,
> >  			       VM_PKT_DATA_INBAND,
> >  			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> > -	if (ret != 0)
> > +	if (ret != 0) {
> > +		/* Reclaim request ID to avoid leak of IDs */
> > +		vmbus_request_addr(&device->channel->requestor, rqst_id);
> >  		return FAILED;
> > +	}
> >  
> >  	t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
> >  	if (t == 0)
> > -- 
> > 2.25.1
> > 
> 
> This patch has landed in linux-next as of next-20200707 and now I can no
> longer boot the WSL2 lightweight VM.
> 
> PS C:\Users\natec> wsl -d ubuntu
> The virtual machine or container was forcefully exited.
> 
> $ git bisect log
> # bad: [5b2a702f85b3285fcde0309aadacc13a36c70fc7] Add linux-next specific files for 20200707
> # good: [bfe91da29bfad9941d5d703d45e29f0812a20724] Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
> git bisect start 'origin/master' 'origin/stable'
> # good: [885913a4d03f7f5fbd2c75121ea8c42f58185cc5] Merge remote-tracking branch 'crypto/master'
> git bisect good 885913a4d03f7f5fbd2c75121ea8c42f58185cc5
> # good: [4a902a00a463f60b1630577a32e142800707c576] Merge remote-tracking branch 'regulator/for-next'
> git bisect good 4a902a00a463f60b1630577a32e142800707c576
> # good: [e48c950eb83e19d532ea49112211b01c6210377a] Merge remote-tracking branch 'thunderbolt/next'
> git bisect good e48c950eb83e19d532ea49112211b01c6210377a
> # good: [0a299abc3a2127d9711517904a1e5c751985b5a5] Merge remote-tracking branch 'rtc/rtc-next'
> git bisect good 0a299abc3a2127d9711517904a1e5c751985b5a5
> # good: [6de62f5629875029fbd8d79d7fa9c45e8dbea966] kcov: make some symbols static
> git bisect good 6de62f5629875029fbd8d79d7fa9c45e8dbea966
> # bad: [9103b615924bf7594a7651a9777e0cf177201dbd] Merge remote-tracking branch 'auxdisplay/auxdisplay'
> git bisect bad 9103b615924bf7594a7651a9777e0cf177201dbd
> # good: [ed0e825a5c0f00aec12f79e8aef4b37dbb5a94f1] Merge remote-tracking branch 'kspp/for-next/kspp'
> git bisect good ed0e825a5c0f00aec12f79e8aef4b37dbb5a94f1
> # good: [563bebf9d7625b579a13b79a4981fdd3097d9bce] Merge remote-tracking branch 'nvmem/for-next'
> git bisect good 563bebf9d7625b579a13b79a4981fdd3097d9bce
> # good: [efd8e353a542e79995681d98a4849eeeb1ce3809] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
> git bisect good efd8e353a542e79995681d98a4849eeeb1ce3809
> # good: [27586ca786a729cda6c807621a1494900a56e7bc] XArray: Handle retry entries within xas_find_marked
> git bisect good 27586ca786a729cda6c807621a1494900a56e7bc
> # bad: [11478f56f20e3be6d11043b501f3090375af4492] hv_netvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening
> git bisect bad 11478f56f20e3be6d11043b501f3090375af4492
> # bad: [8e569d774e1e73afabf1fbf40d11fcb8462ddffa] scsi: storvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardeninggit bisect bad 8e569d774e1e73afabf1fbf40d11fcb8462ddffa
> # first bad commit: [8e569d774e1e73afabf1fbf40d11fcb8462ddffa] scsi: storvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening
> 
> If I revert this commit, everything works fine:
> 
> PS C:\Users\natec> wsl --shutdown
> PS C:\Users\natec> wsl -d ubuntu -- /bin/bash
> nathan@Ryzen-9-3900X:/mnt/c/Users/natec$ cat /proc/version
> Linux version 5.8.0-rc4-next-20200707-microsoft-standard+ (nathan@Ryzen-9-3900X) (gcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #1 SMP Tue Jul 7 16:35:06 MST 2020
> nathan@Ryzen-9-3900X:/mnt/c/Users/natec$ git -C ~/src/linux-next lo -2
> 0ff017dff922 (HEAD -> master) Revert "scsi: storvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening"
> 5b2a702f85b3 (tag: next-20200707, origin/master, origin/HEAD) Add linux-next specific files for 20200707
> nathan@Ryzen-9-3900X:/mnt/c/Users/natec$
> 
> The kernel was built using the following commands:
> 
> $ mkdir -p out/x86_64
> 
> $ curl -LSso out/x86_64/.config https://github.com/microsoft/WSL2-Linux-Kernel/raw/linux-msft-wsl-4.19.y/Microsoft/config-wsl
> 
> $ scripts/config --file out/x86_64/.config -d RAID6_PQ_BENCHMARK -e NET_9P_VIRTIO
> 
> $ make -skj"$(nproc)" O=out/x86_64 olddefconfig bzImage
> 
> I don't really know how to get more information than this as WSL seems
> rather opaque but I am happy to provide any information.

Linux kernel uses Hyper-V's crash reporting facility to spit out
information when it dies. It is said that you can see that information
in the "Event Viewer" program.

(I've never tried this though -- not using WSL2)

Wei.

> 
> Cheers,
> Nathan