* Re: [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
@ 2020-06-29 18:19 Andres Beltran
2020-06-29 19:06 ` Wei Liu
0 siblings, 1 reply; 4+ messages in thread
From: Andres Beltran @ 2020-06-29 18:19 UTC (permalink / raw)
To: Wei Liu, Andres Beltran
Cc: KY Srinivasan, Haiyang Zhang, Stephen Hemminger, linux-hyperv,
linux-kernel, Michael Kelley, parri.andrea
From: linux-hyperv-owner@vger.kernel.org <linux-hyperv-owner@vger.kernel.org> On Behalf
Of Wei Liu. Sent: Friday, June 26, 2020 9:20 AM
> > static int __vmbus_open(struct vmbus_channel *newchannel,
> > void *userdata, u32 userdatalen,
> > void (*onchannelcallback)(void *context), void *context)
> > @@ -122,6 +186,7 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> > u32 send_pages, recv_pages;
> > unsigned long flags;
> > int err;
> > + int rqstor;
> >
> > if (userdatalen > MAX_USER_DEFINED_BYTES)
> > return -EINVAL;
> > @@ -132,6 +197,14 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> > if (newchannel->state != CHANNEL_OPEN_STATE)
> > return -EINVAL;
> >
> > + /* Create and init requestor */
> > + if (newchannel->rqstor_size) {
> > + rqstor = vmbus_alloc_requestor(&newchannel->requestor,
> > + newchannel->rqstor_size);
>
> You can simply use err here to store the return value or even get rid of
> rqstor by doing
Right. I will do that.
> > @@ -937,3 +1014,75 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void
> *buffer,
> > buffer_actual_len, requestid, true);
> > }
> > EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
> > +
> > +/*
> > + * vmbus_next_request_id - Returns a new request id. It is also
> > + * the index at which the guest memory address is stored.
> > + * Uses a spin lock to avoid race conditions.
> > + * @rqstor: Pointer to the requestor struct
> > + * @rqst_add: Guest memory address to be stored in the array
> > + */
> > +u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
> > +{
> > + unsigned long flags;
> > + u64 current_id;
> > +
> > + spin_lock_irqsave(&rqstor->req_lock, flags);
>
> Do you really need the irqsave variant here? I.e. is there really a
> chance this code is reachable from an interrupt handler?
Other VMBus drivers will also need to use this functionality, and
some of them will be called with interrupts disabled. So, I think
we should keep the irqsave variant here.
Andres.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
2020-06-29 18:19 [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening Andres Beltran
@ 2020-06-29 19:06 ` Wei Liu
0 siblings, 0 replies; 4+ messages in thread
From: Wei Liu @ 2020-06-29 19:06 UTC (permalink / raw)
To: Andres Beltran
Cc: Wei Liu, Andres Beltran, KY Srinivasan, Haiyang Zhang,
Stephen Hemminger, linux-hyperv, linux-kernel, Michael Kelley,
parri.andrea
On Mon, Jun 29, 2020 at 06:19:46PM +0000, Andres Beltran wrote:
[...]
> > > EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
> > > +
> > > +/*
> > > + * vmbus_next_request_id - Returns a new request id. It is also
> > > + * the index at which the guest memory address is stored.
> > > + * Uses a spin lock to avoid race conditions.
> > > + * @rqstor: Pointer to the requestor struct
> > > + * @rqst_add: Guest memory address to be stored in the array
> > > + */
> > > +u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
> > > +{
> > > + unsigned long flags;
> > > + u64 current_id;
> > > +
> > > + spin_lock_irqsave(&rqstor->req_lock, flags);
> >
> > Do you really need the irqsave variant here? I.e. is there really a
> > chance this code is reachable from an interrupt handler?
>
> Other VMBus drivers will also need to use this functionality, and
> some of them will be called with interrupts disabled. So, I think
> we should keep the irqsave variant here.
>
Okay. This makes sense.
Wei.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
2020-06-25 15:37 ` [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening Andres Beltran
@ 2020-06-26 13:19 ` Wei Liu
0 siblings, 0 replies; 4+ messages in thread
From: Wei Liu @ 2020-06-26 13:19 UTC (permalink / raw)
To: Andres Beltran
Cc: kys, haiyangz, sthemmin, wei.liu, linux-hyperv, linux-kernel,
mikelley, parri.andrea
On Thu, Jun 25, 2020 at 11:37:21AM -0400, Andres Beltran wrote:
> Currently, VMbus drivers use pointers into guest memory as request IDs
> for interactions with Hyper-V. To be more robust in the face of errors
> or malicious behavior from a compromised Hyper-V, avoid exposing
> guest memory addresses to Hyper-V. Also avoid Hyper-V giving back a
> bad request ID that is then treated as the address of a guest data
> structure with no validation. Instead, encapsulate these memory
> addresses and provide small integers as request IDs.
>
> Signed-off-by: Andres Beltran <lkmlabelt@gmail.com>
> ---
> drivers/hv/channel.c | 149 +++++++++++++++++++++++++++++++++++++++++
> include/linux/hyperv.h | 21 ++++++
> 2 files changed, 170 insertions(+)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 3ebda7707e46..2ea1bfecbfda 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -112,6 +112,70 @@ int vmbus_alloc_ring(struct vmbus_channel *newchannel,
> }
> EXPORT_SYMBOL_GPL(vmbus_alloc_ring);
>
> +/**
> + * request_arr_init - Allocates memory for the requestor array. Each slot
> + * keeps track of the next available slot in the array. Initially, each
> + * slot points to the next one (as in a Linked List). The last slot
> + * does not point to anything, so its value is U64_MAX by default.
> + * @size The size of the array
> + */
> +static u64 *request_arr_init(u32 size)
> +{
> + int i;
> + u64 *req_arr;
> +
> + req_arr = kcalloc(size, sizeof(u64), GFP_KERNEL);
> + if (!req_arr)
> + return NULL;
> +
> + for (i = 0; i < size - 1; i++)
> + req_arr[i] = i + 1;
> +
> + /* Last slot (no more available slots) */
> + req_arr[i] = U64_MAX;
> +
> + return req_arr;
> +}
> +
> +/*
> + * vmbus_alloc_requestor - Initializes @rqstor's fields.
> + * Slot at index 0 is the first free slot.
> + * @size: Size of the requestor array
> + */
> +static int vmbus_alloc_requestor(struct vmbus_requestor *rqstor, u32 size)
> +{
> + u64 *rqst_arr;
> + unsigned long *bitmap;
> +
> + rqst_arr = request_arr_init(size);
> + if (!rqst_arr)
> + return -ENOMEM;
> +
> + bitmap = bitmap_zalloc(size, GFP_KERNEL);
> + if (!bitmap) {
> + kfree(rqst_arr);
> + return -ENOMEM;
> + }
> +
> + rqstor->req_arr = rqst_arr;
> + rqstor->req_bitmap = bitmap;
> + rqstor->size = size;
> + rqstor->next_request_id = 0;
> + spin_lock_init(&rqstor->req_lock);
> +
> + return 0;
> +}
> +
> +/*
> + * vmbus_free_requestor - Frees memory allocated for @rqstor
> + * @rqstor: Pointer to the requestor struct
> + */
> +static void vmbus_free_requestor(struct vmbus_requestor *rqstor)
> +{
> + kfree(rqstor->req_arr);
> + bitmap_free(rqstor->req_bitmap);
> +}
> +
> static int __vmbus_open(struct vmbus_channel *newchannel,
> void *userdata, u32 userdatalen,
> void (*onchannelcallback)(void *context), void *context)
> @@ -122,6 +186,7 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> u32 send_pages, recv_pages;
> unsigned long flags;
> int err;
> + int rqstor;
>
> if (userdatalen > MAX_USER_DEFINED_BYTES)
> return -EINVAL;
> @@ -132,6 +197,14 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> if (newchannel->state != CHANNEL_OPEN_STATE)
> return -EINVAL;
>
> + /* Create and init requestor */
> + if (newchannel->rqstor_size) {
> + rqstor = vmbus_alloc_requestor(&newchannel->requestor,
> + newchannel->rqstor_size);
You can simply use err here to store the return value or even get rid of
rqstor by doing
if (vmbus_alloc_requestor(...))
> + if (rqstor)
> + return -ENOMEM;
> + }
> +
> newchannel->state = CHANNEL_OPENING_STATE;
> newchannel->onchannel_callback = onchannelcallback;
> newchannel->channel_callback_context = context;
> @@ -228,6 +301,7 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> error_clean_ring:
> hv_ringbuffer_cleanup(&newchannel->outbound);
> hv_ringbuffer_cleanup(&newchannel->inbound);
> + vmbus_free_requestor(&newchannel->requestor);
> newchannel->state = CHANNEL_OPEN_STATE;
> return err;
> }
> @@ -703,6 +777,9 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
> channel->ringbuffer_gpadlhandle = 0;
> }
>
> + if (!ret)
> + vmbus_free_requestor(&channel->requestor);
> +
> return ret;
> }
>
> @@ -937,3 +1014,75 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
> buffer_actual_len, requestid, true);
> }
> EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
> +
> +/*
> + * vmbus_next_request_id - Returns a new request id. It is also
> + * the index at which the guest memory address is stored.
> + * Uses a spin lock to avoid race conditions.
> + * @rqstor: Pointer to the requestor struct
> + * @rqst_add: Guest memory address to be stored in the array
> + */
> +u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
> +{
> + unsigned long flags;
> + u64 current_id;
> +
> + spin_lock_irqsave(&rqstor->req_lock, flags);
Do you really need the irqsave variant here? I.e. is there really a
chance this code is reachable from an interrupt handler?
Wei.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
2020-06-25 15:37 [PATCH 0/3] Drivers: hv: vmbus: vmbus_requestor data structure Andres Beltran
@ 2020-06-25 15:37 ` Andres Beltran
2020-06-26 13:19 ` Wei Liu
0 siblings, 1 reply; 4+ messages in thread
From: Andres Beltran @ 2020-06-25 15:37 UTC (permalink / raw)
To: kys, haiyangz, sthemmin, wei.liu
Cc: linux-hyperv, linux-kernel, mikelley, parri.andrea, Andres Beltran
Currently, VMbus drivers use pointers into guest memory as request IDs
for interactions with Hyper-V. To be more robust in the face of errors
or malicious behavior from a compromised Hyper-V, avoid exposing
guest memory addresses to Hyper-V. Also avoid Hyper-V giving back a
bad request ID that is then treated as the address of a guest data
structure with no validation. Instead, encapsulate these memory
addresses and provide small integers as request IDs.
Signed-off-by: Andres Beltran <lkmlabelt@gmail.com>
---
drivers/hv/channel.c | 149 +++++++++++++++++++++++++++++++++++++++++
include/linux/hyperv.h | 21 ++++++
2 files changed, 170 insertions(+)
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 3ebda7707e46..2ea1bfecbfda 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -112,6 +112,70 @@ int vmbus_alloc_ring(struct vmbus_channel *newchannel,
}
EXPORT_SYMBOL_GPL(vmbus_alloc_ring);
+/**
+ * request_arr_init - Allocates memory for the requestor array. Each slot
+ * keeps track of the next available slot in the array. Initially, each
+ * slot points to the next one (as in a Linked List). The last slot
+ * does not point to anything, so its value is U64_MAX by default.
+ * @size The size of the array
+ */
+static u64 *request_arr_init(u32 size)
+{
+ int i;
+ u64 *req_arr;
+
+ req_arr = kcalloc(size, sizeof(u64), GFP_KERNEL);
+ if (!req_arr)
+ return NULL;
+
+ for (i = 0; i < size - 1; i++)
+ req_arr[i] = i + 1;
+
+ /* Last slot (no more available slots) */
+ req_arr[i] = U64_MAX;
+
+ return req_arr;
+}
+
+/*
+ * vmbus_alloc_requestor - Initializes @rqstor's fields.
+ * Slot at index 0 is the first free slot.
+ * @size: Size of the requestor array
+ */
+static int vmbus_alloc_requestor(struct vmbus_requestor *rqstor, u32 size)
+{
+ u64 *rqst_arr;
+ unsigned long *bitmap;
+
+ rqst_arr = request_arr_init(size);
+ if (!rqst_arr)
+ return -ENOMEM;
+
+ bitmap = bitmap_zalloc(size, GFP_KERNEL);
+ if (!bitmap) {
+ kfree(rqst_arr);
+ return -ENOMEM;
+ }
+
+ rqstor->req_arr = rqst_arr;
+ rqstor->req_bitmap = bitmap;
+ rqstor->size = size;
+ rqstor->next_request_id = 0;
+ spin_lock_init(&rqstor->req_lock);
+
+ return 0;
+}
+
+/*
+ * vmbus_free_requestor - Frees memory allocated for @rqstor
+ * @rqstor: Pointer to the requestor struct
+ */
+static void vmbus_free_requestor(struct vmbus_requestor *rqstor)
+{
+ kfree(rqstor->req_arr);
+ bitmap_free(rqstor->req_bitmap);
+}
+
static int __vmbus_open(struct vmbus_channel *newchannel,
void *userdata, u32 userdatalen,
void (*onchannelcallback)(void *context), void *context)
@@ -122,6 +186,7 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
u32 send_pages, recv_pages;
unsigned long flags;
int err;
+ int rqstor;
if (userdatalen > MAX_USER_DEFINED_BYTES)
return -EINVAL;
@@ -132,6 +197,14 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
if (newchannel->state != CHANNEL_OPEN_STATE)
return -EINVAL;
+ /* Create and init requestor */
+ if (newchannel->rqstor_size) {
+ rqstor = vmbus_alloc_requestor(&newchannel->requestor,
+ newchannel->rqstor_size);
+ if (rqstor)
+ return -ENOMEM;
+ }
+
newchannel->state = CHANNEL_OPENING_STATE;
newchannel->onchannel_callback = onchannelcallback;
newchannel->channel_callback_context = context;
@@ -228,6 +301,7 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
error_clean_ring:
hv_ringbuffer_cleanup(&newchannel->outbound);
hv_ringbuffer_cleanup(&newchannel->inbound);
+ vmbus_free_requestor(&newchannel->requestor);
newchannel->state = CHANNEL_OPEN_STATE;
return err;
}
@@ -703,6 +777,9 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
channel->ringbuffer_gpadlhandle = 0;
}
+ if (!ret)
+ vmbus_free_requestor(&channel->requestor);
+
return ret;
}
@@ -937,3 +1014,75 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
buffer_actual_len, requestid, true);
}
EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
+
+/*
+ * vmbus_next_request_id - Returns a new request id. It is also
+ * the index at which the guest memory address is stored.
+ * Uses a spin lock to avoid race conditions.
+ * @rqstor: Pointer to the requestor struct
+ * @rqst_add: Guest memory address to be stored in the array
+ */
+u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
+{
+ unsigned long flags;
+ u64 current_id;
+
+ spin_lock_irqsave(&rqstor->req_lock, flags);
+ current_id = rqstor->next_request_id;
+
+ /* Requestor array is full */
+ if (current_id >= rqstor->size) {
+ current_id = VMBUS_RQST_ERROR;
+ goto exit;
+ }
+
+ rqstor->next_request_id = rqstor->req_arr[current_id];
+ rqstor->req_arr[current_id] = rqst_addr;
+
+ /* The already held spin lock provides atomicity */
+ bitmap_set(rqstor->req_bitmap, current_id, 1);
+
+exit:
+ spin_unlock_irqrestore(&rqstor->req_lock, flags);
+ return current_id;
+}
+EXPORT_SYMBOL_GPL(vmbus_next_request_id);
+
+/*
+ * vmbus_request_addr - Returns the memory address stored at @trans_id
+ * in @rqstor. Uses a spin lock to avoid race conditions.
+ * @rqstor: Pointer to the requestor struct
+ * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
+ * next request id.
+ */
+u64 vmbus_request_addr(struct vmbus_requestor *rqstor, u64 trans_id)
+{
+ unsigned long flags;
+ u64 req_addr;
+
+ spin_lock_irqsave(&rqstor->req_lock, flags);
+
+ /* Invalid trans_id */
+ if (trans_id >= rqstor->size) {
+ req_addr = VMBUS_RQST_ERROR;
+ goto exit;
+ }
+
+ /* Invalid trans_id: empty slot */
+ if (!test_bit(trans_id, rqstor->req_bitmap)) {
+ req_addr = VMBUS_RQST_ERROR;
+ goto exit;
+ }
+
+ req_addr = rqstor->req_arr[trans_id];
+ rqstor->req_arr[trans_id] = rqstor->next_request_id;
+ rqstor->next_request_id = trans_id;
+
+ /* The already held spin lock provides atomicity */
+ bitmap_clear(rqstor->req_bitmap, trans_id, 1);
+
+exit:
+ spin_unlock_irqrestore(&rqstor->req_lock, flags);
+ return req_addr;
+}
+EXPORT_SYMBOL_GPL(vmbus_request_addr);
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 38100e80360a..c509d20ab7db 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -716,6 +716,21 @@ enum vmbus_device_type {
HV_UNKNOWN,
};
+/*
+ * Provides request ids for VMBus. Encapsulates guest memory
+ * addresses and stores the next available slot in req_arr
+ * to generate new ids in constant time.
+ */
+struct vmbus_requestor {
+ u64 *req_arr;
+ unsigned long *req_bitmap; /* is a given slot available? */
+ u32 size;
+ u64 next_request_id;
+ spinlock_t req_lock; /* provides atomicity */
+};
+
+#define VMBUS_RQST_ERROR U64_MAX
+
struct vmbus_device {
u16 dev_type;
guid_t guid;
@@ -940,8 +955,14 @@ struct vmbus_channel {
u32 fuzz_testing_interrupt_delay;
u32 fuzz_testing_message_delay;
+ /* request/transaction ids for VMBus */
+ struct vmbus_requestor requestor;
+ u32 rqstor_size;
};
+u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr);
+u64 vmbus_request_addr(struct vmbus_requestor *rqstor, u64 trans_id);
+
static inline bool is_hvsock_channel(const struct vmbus_channel *c)
{
return !!(c->offermsg.offer.chn_flags &
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2020-06-29 19:06 ` Wei Liu
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2020-06-25 15:37 [PATCH 0/3] Drivers: hv: vmbus: vmbus_requestor data structure Andres Beltran
2020-06-25 15:37 ` [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening Andres Beltran
2020-06-26 13:19 ` Wei Liu
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