tpm: Fix off-by-one error when calculating event size

tpm_log_event_raw() allocates a buffer for the EFI_TCG2_EVENT structure
that is one byte larger than necessary, and sets event->Size accordingly.
The result of this is that the event data recorded in the log differs
from the data that is measured to the TPM (it has an extra zero byte
at the end).

src/tpm.c

@@ -131,8 +131,10 @@ static EFI_STATUS tpm_log_event_raw(EFI_PHYSICAL_ADDRESS buf, UINTN size,
 #endif
 	} else if (tpm2) {
 		EFI_TCG2_EVENT *event;
+		UINTN event_size = sizeof(*event) - sizeof(event->Event) +
+			logsize;
 
-		event = AllocatePool(sizeof(*event) + logsize);
+		event = AllocatePool(event_size);
 		if (!event) {
 			perror(L"Unable to allocate event structure\n");
 			return EFI_OUT_OF_RESOURCES;
@@ -142,7 +144,7 @@ static EFI_STATUS tpm_log_event_raw(EFI_PHYSICAL_ADDRESS buf, UINTN size,
 		event->Header.HeaderVersion = 1;
 		event->Header.PCRIndex = pcr;
 		event->Header.EventType = type;
-		event->Size = sizeof(*event) - sizeof(event->Event) + logsize + 1;
+		event->Size = event_size;
 		CopyMem(event->Event, (VOID *)log, logsize);
 		if (hash) {
 			/* TPM 2 systems will generate the appropriate hash