From 957e4ee54b35198a627c4a52542d25235d9a920b Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Mon, 24 Aug 2026 13:15:42 +1000
Subject: [PATCH] [client] lgmp: validate frame message alignment

---
 client/tests/lgmp_frame_test.c     | 11 +++++++----
 client/tests/lgmp_transport_test.c |  3 ++-
 client/transports/LGMP/lgmp.c      |  6 ++++++
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/client/tests/lgmp_frame_test.c b/client/tests/lgmp_frame_test.c
index a04fc78f..6a4c65ee 100644
--- a/client/tests/lgmp_frame_test.c
+++ b/client/tests/lgmp_frame_test.c
@@ -97,11 +97,12 @@ static bool waitForEmpty(TestState * state)
   return false;
 }
 
-static bool allocMemory(TestState * state, uint32_t size,
+static bool allocMemory(TestState * state, uint32_t size, uint32_t alignment,
     PLGMPMemory * memory, void ** pointer)
 {
   CHECK(state->allocationCount < TEST_MAX_ALLOCS);
-  CHECK(lgmpHostMemAlloc(state->host, size, memory) == LGMP_OK);
+  CHECK(lgmpHostMemAllocAligned(
+        state->host, size, alignment, memory) == LGMP_OK);
   state->allocations[state->allocationCount++] = *memory;
   *pointer = lgmpHostMemPtr(*memory);
   return true;
@@ -112,7 +113,8 @@ static bool newFrame(TestState * state, uint32_t serial, TestFrame * result)
   const uint32_t size = sizeof(KVMFRFrame) + sizeof(FrameBuffer) +
     TEST_FRAME_DATA;
   void * pointer;
-  CHECK(allocMemory(state, size, &result->memory, &pointer));
+  CHECK(allocMemory(state, size, _Alignof(KVMFRFrame),
+        &result->memory, &pointer));
 
   result->wire = pointer;
   result->wire->formatVer     = 1;
@@ -199,7 +201,8 @@ static bool testMalformed(TestState * state)
 
   PLGMPMemory shortMemory;
   void * shortPointer;
-  CHECK(allocMemory(state, sizeof(KVMFRFrame) - 4, &shortMemory,
+  CHECK(allocMemory(state, sizeof(KVMFRFrame) - 4, _Alignof(uint32_t),
+        &shortMemory,
         &shortPointer));
   CHECK(lgmpHostQueuePost(state->queues[0], 0, shortMemory) == LGMP_OK);
   LG_TransportFrame result;
diff --git a/client/tests/lgmp_transport_test.c b/client/tests/lgmp_transport_test.c
index 0b5ba7c9..b1939a08 100644
--- a/client/tests/lgmp_transport_test.c
+++ b/client/tests/lgmp_transport_test.c
@@ -381,7 +381,8 @@ int main(void)
   };
   const uint32_t frameSize =
     sizeof(KVMFRFrame) + sizeof(FrameBuffer) + sizeof(uint32_t);
-  CHECK(lgmpHostMemAlloc(host, frameSize, &frameMemory) == LGMP_OK);
+  CHECK(lgmpHostMemAllocAligned(host, frameSize, _Alignof(KVMFRFrame),
+        &frameMemory) == LGMP_OK);
   KVMFRFrame * wireFrame = lgmpHostMemPtr(frameMemory);
   wireFrame->formatVer   = 1;
   wireFrame->frameSerial = 1;
diff --git a/client/transports/LGMP/lgmp.c b/client/transports/LGMP/lgmp.c
index 02029c5b..aef50b8e 100644
--- a/client/transports/LGMP/lgmp.c
+++ b/client/transports/LGMP/lgmp.c
@@ -1786,6 +1786,12 @@ static bool lgmp_validateFrameMessage(LG_Transport * this,
     return false;
   }
 
+  if ((uintptr_t)message->message.mem % _Alignof(KVMFRFrame))
+  {
+    DEBUG_ERROR("LGMP frame payload is not correctly aligned");
+    return false;
+  }
+
   memcpy(&message->lease->snapshot, message->message.mem,
       sizeof(message->lease->snapshot));
   const KVMFRFrame * frame = &message->lease->snapshot;