[PATCH 5.10 51/73] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening

From: Andres Beltran lkmlabelt@gmail.com

[ Upstream commit e8b7db38449ac5b950a3f00519171c4be3e226ff ]

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 Stable-dep-of: 9cae43da9867 ("hv_netvsc: Register VF in netvsc_probe if NET_DEVICE_REGISTER missed") Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hv/channel.c | 174 ++++++++++++++++++++++++++++++++++++-- drivers/hv/hyperv_vmbus.h | 3 +- drivers/hv/ring_buffer.c | 29 ++++++- include/linux/hyperv.h | 22 +++++ 4 files changed, 219 insertions(+), 9 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index f064fa6ef181a..a59ab2f3d68e1 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 @@ 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; } @@ -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 7845fa5de79e9..601660bca5d47 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -180,7 +180,8 @@ 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 7ed6fad3fa8ff..a0ba6ac487368 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -261,7 +261,8 @@ EXPORT_SYMBOL_GPL(hv_ringbuffer_spinlock_busy);

/* 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; @@ -271,6 +272,8 @@ 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; @@ -313,6 +316,23 @@ 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);

@@ -332,8 +352,13 @@ 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; } diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index eada4d8d65879..4cb65a79d92f6 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -764,6 +764,22 @@ 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_NO_RQSTOR U64_MAX +#define VMBUS_RQST_ERROR (U64_MAX - 1) + struct vmbus_device { u16 dev_type; guid_t guid; @@ -988,8 +1004,14 @@ 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 &