From e8b7db38449ac5b950a3f00519171c4be3e226ff Mon Sep 17 00:00:00 2001 From: Andres Beltran Date: Mon, 9 Nov 2020 11:04:00 +0100 Subject: 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 Co-developed-by: Andrea Parri (Microsoft) Signed-off-by: Andrea Parri (Microsoft) Reviewed-by: Michael Kelley Reviewed-by: Wei Liu Link: https://lore.kernel.org/r/20201109100402.8946-2-parri.andrea@gmail.com Signed-off-by: Wei Liu --- drivers/hv/ring_buffer.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) (limited to 'drivers/hv/ring_buffer.c') 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; } -- cgit v1.2.3