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authorAndres Beltran <lkmlabelt@gmail.com>2020-11-09 11:04:00 +0100
committerWei Liu <wei.liu@kernel.org>2020-11-17 10:51:06 +0000
commite8b7db38449ac5b950a3f00519171c4be3e226ff (patch)
tree257903993b84723c09238c6963d022a9d857520f /drivers/hv
parent09162bc32c880a791c6c0668ce0745cf7958f576 (diff)
Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
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> Co-developed-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Reviewed-by: Wei Liu <wei.liu@kernel.org> Link: https://lore.kernel.org/r/20201109100402.8946-2-parri.andrea@gmail.com Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'drivers/hv')
-rw-r--r--drivers/hv/channel.c174
-rw-r--r--drivers/hv/hyperv_vmbus.h3
-rw-r--r--drivers/hv/ring_buffer.c29
3 files changed, 197 insertions, 9 deletions
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index fbdda9938039..6fb0c76bfbf8 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -503,6 +503,70 @@ int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
}
EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);
+/**
+ * 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.
+ * 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)
@@ -523,6 +587,12 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
if (newchannel->state != CHANNEL_OPEN_STATE)
return -EINVAL;
+ /* Create and init requestor */
+ if (newchannel->rqstor_size) {
+ if (vmbus_alloc_requestor(&newchannel->requestor, newchannel->rqstor_size))
+ return -ENOMEM;
+ }
+
newchannel->state = CHANNEL_OPENING_STATE;
newchannel->onchannel_callback = onchannelcallback;
newchannel->channel_callback_context = context;
@@ -626,6 +696,7 @@ error_free_gpadl:
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;
}
@@ -808,6 +879,9 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
channel->ringbuffer_gpadlhandle = 0;
}
+ if (!ret)
+ vmbus_free_requestor(&channel->requestor);
+
return ret;
}
@@ -888,7 +962,7 @@ int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
/* in 8-bytes granularity */
desc.offset8 = sizeof(struct vmpacket_descriptor) >> 3;
desc.len8 = (u16)(packetlen_aligned >> 3);
- desc.trans_id = requestid;
+ desc.trans_id = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
bufferlist[0].iov_base = &desc;
bufferlist[0].iov_len = sizeof(struct vmpacket_descriptor);
@@ -897,7 +971,7 @@ int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
bufferlist[2].iov_base = &aligned_data;
bufferlist[2].iov_len = (packetlen_aligned - packetlen);
- return hv_ringbuffer_write(channel, bufferlist, num_vecs);
+ return hv_ringbuffer_write(channel, bufferlist, num_vecs, requestid);
}
EXPORT_SYMBOL(vmbus_sendpacket);
@@ -939,7 +1013,7 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
desc.flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
desc.dataoffset8 = descsize >> 3; /* in 8-bytes granularity */
desc.length8 = (u16)(packetlen_aligned >> 3);
- desc.transactionid = requestid;
+ desc.transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
desc.reserved = 0;
desc.rangecount = pagecount;
@@ -956,7 +1030,7 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
bufferlist[2].iov_base = &aligned_data;
bufferlist[2].iov_len = (packetlen_aligned - packetlen);
- return hv_ringbuffer_write(channel, bufferlist, 3);
+ return hv_ringbuffer_write(channel, bufferlist, 3, requestid);
}
EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer);
@@ -983,7 +1057,7 @@ int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
desc->flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
desc->dataoffset8 = desc_size >> 3; /* in 8-bytes granularity */
desc->length8 = (u16)(packetlen_aligned >> 3);
- desc->transactionid = requestid;
+ desc->transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
desc->reserved = 0;
desc->rangecount = 1;
@@ -994,7 +1068,7 @@ int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
bufferlist[2].iov_base = &aligned_data;
bufferlist[2].iov_len = (packetlen_aligned - packetlen);
- return hv_ringbuffer_write(channel, bufferlist, 3);
+ return hv_ringbuffer_write(channel, bufferlist, 3, requestid);
}
EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);
@@ -1042,3 +1116,91 @@ 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;
+ const struct vmbus_channel *channel =
+ container_of(rqstor, const struct vmbus_channel, requestor);
+
+ /* Check rqstor has been initialized */
+ if (!channel->rqstor_size)
+ return VMBUS_NO_RQSTOR;
+
+ spin_lock_irqsave(&rqstor->req_lock, flags);
+ current_id = rqstor->next_request_id;
+
+ /* Requestor array is full */
+ if (current_id >= rqstor->size) {
+ spin_unlock_irqrestore(&rqstor->req_lock, flags);
+ return VMBUS_RQST_ERROR;
+ }
+
+ 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);
+
+ spin_unlock_irqrestore(&rqstor->req_lock, flags);
+
+ /*
+ * Cannot return an ID of 0, which is reserved for an unsolicited
+ * message from Hyper-V.
+ */
+ return current_id + 1;
+}
+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;
+ const struct vmbus_channel *channel =
+ container_of(rqstor, const struct vmbus_channel, requestor);
+
+ /* Check rqstor has been initialized */
+ if (!channel->rqstor_size)
+ return VMBUS_NO_RQSTOR;
+
+ /* Hyper-V can send an unsolicited message with ID of 0 */
+ if (!trans_id)
+ return trans_id;
+
+ spin_lock_irqsave(&rqstor->req_lock, flags);
+
+ /* Data corresponding to trans_id is stored at trans_id - 1 */
+ trans_id--;
+
+ /* Invalid trans_id */
+ if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap)) {
+ spin_unlock_irqrestore(&rqstor->req_lock, flags);
+ return VMBUS_RQST_ERROR;
+ }
+
+ 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);
+
+ spin_unlock_irqrestore(&rqstor->req_lock, flags);
+ return req_addr;
+}
+EXPORT_SYMBOL_GPL(vmbus_request_addr);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 40e2b9f91163..02f3e8988836 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -179,7 +179,8 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
int hv_ringbuffer_write(struct vmbus_channel *channel,
- const struct kvec *kv_list, u32 kv_count);
+ const struct kvec *kv_list, u32 kv_count,
+ u64 requestid);
int hv_ringbuffer_read(struct vmbus_channel *channel,
void *buffer, u32 buflen, u32 *buffer_actual_len,
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 356e22159e83..35833d4d1a1d 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -248,7 +248,8 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
/* Write to the ring buffer. */
int hv_ringbuffer_write(struct vmbus_channel *channel,
- const struct kvec *kv_list, u32 kv_count)
+ const struct kvec *kv_list, u32 kv_count,
+ u64 requestid)
{
int i;
u32 bytes_avail_towrite;
@@ -258,6 +259,8 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
u64 prev_indices;
unsigned long flags;
struct hv_ring_buffer_info *outring_info = &channel->outbound;
+ struct vmpacket_descriptor *desc = kv_list[0].iov_base;
+ u64 rqst_id = VMBUS_NO_RQSTOR;
if (channel->rescind)
return -ENODEV;
@@ -300,6 +303,23 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
kv_list[i].iov_len);
}
+ /*
+ * Allocate the request ID after the data has been copied into the
+ * ring buffer. Once this request ID is allocated, the completion
+ * path could find the data and free it.
+ */
+
+ if (desc->flags == VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED) {
+ rqst_id = vmbus_next_request_id(&channel->requestor, requestid);
+ if (rqst_id == VMBUS_RQST_ERROR) {
+ spin_unlock_irqrestore(&outring_info->ring_lock, flags);
+ pr_err("No request id available\n");
+ return -EAGAIN;
+ }
+ }
+ desc = hv_get_ring_buffer(outring_info) + old_write;
+ desc->trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id;
+
/* Set previous packet start */
prev_indices = hv_get_ring_bufferindices(outring_info);
@@ -319,8 +339,13 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
hv_signal_on_write(old_write, channel);
- if (channel->rescind)
+ if (channel->rescind) {
+ if (rqst_id != VMBUS_NO_RQSTOR) {
+ /* Reclaim request ID to avoid leak of IDs */
+ vmbus_request_addr(&channel->requestor, rqst_id);
+ }
return -ENODEV;
+ }
return 0;
}