Date:   Tue, 7 Jul 2020 16:47:00 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     t-mabelt@...rosoft.com
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com,
        parri.andrea@...il.com, Andres Beltran <lkmlabelt@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org
Subject: Re: [PATCH v4 2/3] scsi: storvsc: Use vmbus_requestor to generate
 transaction IDs for VMBus hardening

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@...ux.ibm.com>
> Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
> Cc: linux-scsi@...r.kernel.org
> Signed-off-by: Andres Beltran <lkmlabelt@...il.com>
> Reviewed-by: Michael Kelley <mikelley@...rosoft.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@...en-9-3900X:/mnt/c/Users/natec$ cat /proc/version
Linux version 5.8.0-rc4-next-20200707-microsoft-standard+ (nathan@...en-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@...en-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@...en-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.

Cheers,
Nathan

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