fw-update: reject mismatched EID in ItemUpdateManager dispatch

ItemUpdateManager::handleRequest declared its eid parameter as
mctp_eid_t /*eid*/ and dispatched purely on command. Combined with
AggregateUpdateManager iterating updateManagers in SoftwareIdentifier
(i.e. eid-then-component) order, whichever active ItemUpdateManager
came first claimed every FW-update response regardless of the inbound
EID. Two concurrent target updates on different EIDs would have all
responses funneled to the lower-EID manager.

Concretely: with an update on EID 12 in flight, starting an update
on EID 10 created ItemUpdateManager(10). EID 12's apply_complete was
then consumed by deviceUpdater10 and logged as if it belonged to EID
10 (device_updater.cpp:858 uses the deviceUpdater's own eid member).
EID 10 timed out on ActivateFirmware while EID 12's deviceUpdater
state was corrupted by the misrouted messages.

The per-ItemUpdateManager state (deviceUpdater, packageMap, dupFd,
inProgressActivation, ...) is already independent, and the shared
Handler<Request>/InstanceIdDb demux BMC->FD responses by
(eid, instanceId), so concurrent multi-EID target updates work
correctly once the responder path stops the cross-EID misrouting.

Add an explicit eid != this->eid early-return that yields
PLDM_FWUP_COMMAND_NOT_EXPECTED, letting AggregateUpdateManager fall
through to the next manager. Fold the !deviceUpdater branch into the
same early-return since it returns the same encoded response, and
convert the placement-new calls to std::start_lifetime_as<> to match
the rest of the codebase.

Tested on nvl32-obmc:
- Full bundle multipart update.
- Single target update.
- Back to back single-target updates.
- Full bundle update followed by a target update (previously flooded
  the journal with "invalid state when updating progress" and served
  data from the stale bundle DeviceUpdater; now routed correctly).
- Target update on a second PLDM device while an update on another
  device is in progress: both complete successfully.
- Target update on the same device while its update is in progress:
  rejected as expected.

Signed-off-by: Dhruv Rathi <rathidhruv04@gmail.com>
Change-Id: I390c54c82fc6405de37a06af6a8d0e80d31735d3

fw-update/item_update_manager.cpp

diff --git a/fw-update/item_update_manager.cpp b/fw-update/item_update_manager.cpp
index 4e5def4..2d014dd 100644
--- a/fw-update/item_update_manager.cpp
+++ b/fw-update/item_update_manager.cpp
@@ -1,6 +1,7 @@
 #include "item_update_manager.hpp"
 
 #include "activation.hpp"
+#include "common/start_lifetime_as.hpp"
 #include "common/utils.hpp"
 #include "package_parser.hpp"
 
@@ -173,47 +174,42 @@
     return;
 }
 
-Response ItemUpdateManager::handleRequest(mctp_eid_t /*eid*/, uint8_t command,
-                                          const pldm_msg* request,
-                                          size_t reqMsgLen)
+Response ItemUpdateManager::handleRequest(
+    mctp_eid_t eid, uint8_t command, const pldm_msg* request, size_t reqMsgLen)
 {
     Response response(sizeof(pldm_msg), 0);
-    if (deviceUpdater)
+    if (eid != this->eid || !deviceUpdater)
     {
-        if (command == PLDM_REQUEST_FIRMWARE_DATA)
-        {
-            return deviceUpdater->requestFwData(request, reqMsgLen);
-        }
-        else if (command == PLDM_TRANSFER_COMPLETE)
-        {
-            return deviceUpdater->transferComplete(request, reqMsgLen);
-        }
-        else if (command == PLDM_VERIFY_COMPLETE)
-        {
-            return deviceUpdater->verifyComplete(request, reqMsgLen);
-        }
-        else if (command == PLDM_APPLY_COMPLETE)
-        {
-            return deviceUpdater->applyComplete(request, reqMsgLen);
-        }
-        else
-        {
-            auto ptr = new (response.data()) pldm_msg;
-            auto rc = encode_cc_only_resp(
-                request->hdr.instance_id, request->hdr.type,
-                request->hdr.command, PLDM_ERROR_INVALID_DATA, ptr);
-            assert(rc == PLDM_SUCCESS);
-        }
-    }
-    else
-    {
-        auto ptr = new (response.data()) pldm_msg;
+        auto ptr = std::start_lifetime_as<pldm_msg>(response.data());
         auto rc = encode_cc_only_resp(request->hdr.instance_id,
-                                      request->hdr.type, +request->hdr.command,
+                                      request->hdr.type, request->hdr.command,
                                       PLDM_FWUP_COMMAND_NOT_EXPECTED, ptr);
         assert(rc == PLDM_SUCCESS);
+        return response;
     }
 
+    if (command == PLDM_REQUEST_FIRMWARE_DATA)
+    {
+        return deviceUpdater->requestFwData(request, reqMsgLen);
+    }
+    else if (command == PLDM_TRANSFER_COMPLETE)
+    {
+        return deviceUpdater->transferComplete(request, reqMsgLen);
+    }
+    else if (command == PLDM_VERIFY_COMPLETE)
+    {
+        return deviceUpdater->verifyComplete(request, reqMsgLen);
+    }
+    else if (command == PLDM_APPLY_COMPLETE)
+    {
+        return deviceUpdater->applyComplete(request, reqMsgLen);
+    }
+
+    auto ptr = std::start_lifetime_as<pldm_msg>(response.data());
+    auto rc =
+        encode_cc_only_resp(request->hdr.instance_id, request->hdr.type,
+                            request->hdr.command, PLDM_ERROR_INVALID_DATA, ptr);
+    assert(rc == PLDM_SUCCESS);
     return response;
 }