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Drivers: hv: vmbus: Fix handling of messages with transaction ID of zero 

vmbus_request_addr() returns 0 (zero) if the transaction ID passed
to as argument is 0.  This is unfortunate for two reasons: first,
netvsc_send_completion() does not check for a NULL cmd_rqst (before
dereferencing the corresponding NVSP message); second, 0 is a *valid*
value of cmd_rqst in netvsc_send_tx_complete(), cf. the call of
vmbus_sendpacket() in netvsc_send_pkt().

vmbus_request_addr() has included the code in question since its
introduction with commit e8b7db3844 ("Drivers: hv: vmbus: Add
vmbus_requestor data structure for VMBus hardening"); such code was
motivated by the early use of vmbus_requestor by hv_storvsc.  Since
hv_storvsc moved to a tag-based mechanism to generate and retrieve
transaction IDs with commit bf5fd8cae3 ("scsi: storvsc: Use
blk_mq_unique_tag() to generate requestIDs"), vmbus_request_addr()
can be modified to return VMBUS_RQST_ERROR if the ID is 0.  This
change solves the issues in hv_netvsc (and makes the handling of
messages with transaction ID of 0 consistent with the semantics
"the ID is not contained in the requestor/invalid ID").

vmbus_next_request_id(), vmbus_request_addr() should still reserve
the ID of 0 for Hyper-V, because Hyper-V will "ignore" (not respond
to) VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED packets/requests with
transaction ID of 0 from the guest.

Fixes: bf5fd8cae3 ("scsi: storvsc: Use blk_mq_unique_tag() to generate requestIDs")
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220419122325.10078-2-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Andrea Parri (Microsoft) 2022-04-19 14:23:20 +02:00 committed by Wei Liu
parent 08e61e861a
commit 82cd4bacff
1 changed files with 4 additions and 2 deletions
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6
drivers/hv/channel.c
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@ -1245,7 +1245,9 @@ u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
/*
* Cannot return an ID of 0, which is reserved for an unsolicited
* message from Hyper-V.
* message from Hyper-V; Hyper-V does not acknowledge (respond to)
* VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED requests with ID of
* 0 sent by the guest.
*/
return current_id + 1;
}
@ -1270,7 +1272,7 @@ u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
/* Hyper-V can send an unsolicited message with ID of 0 */
if (!trans_id)
return trans_id;
return VMBUS_RQST_ERROR;
spin_lock_irqsave(&rqstor->req_lock, flags);