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Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening

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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>
This commit is contained in:
Andres Beltran 2020-11-09 11:04:00 +01:00 • committed by Wei Liu
parent 09162bc32c
commit e8b7db3844
4 changed files with 219 additions and 9 deletions
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22
include/linux/hyperv.h
View file

@ -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 &