commit 778c0905f9a3a2f029cc9d4fe262ba3e61d35cd8
author Frederick Mayle <fmayle@google.com> Fri May 27 01:14:57 2022 +0000
committer Frederick Mayle <fmayle@google.com> Tue May 31 21:32:34 2022 +0000
tree e984287bbf2275181e8b986774c73172b3c45b2b
parent fbc2aee950be80a0b36375c1d3d270e6d26d2b6d

binder: Tweak overflow check for readability

Test: TH
Change-Id: I01a9edd997095c03a35ceb4d75b3bb6df1863704

libs/binder/RpcState.cpp

diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index 4ef9cd8..2a8e9c1 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -493,14 +493,13 @@
         }
     }
 
-    LOG_ALWAYS_FATAL_IF(std::numeric_limits<int32_t>::max() - sizeof(RpcWireHeader) -
-                                        sizeof(RpcWireTransaction) <
-                                data.dataSize(),
+    uint32_t bodySize;
+    LOG_ALWAYS_FATAL_IF(__builtin_add_overflow(sizeof(RpcWireTransaction), data.dataSize(),
+                                               &bodySize),
                         "Too much data %zu", data.dataSize());
-
     RpcWireHeader command{
             .command = RPC_COMMAND_TRANSACT,
-            .bodySize = static_cast<uint32_t>(sizeof(RpcWireTransaction) + data.dataSize()),
+            .bodySize = bodySize,
     };
 
     RpcWireTransaction transaction{
@@ -940,14 +939,12 @@
         replyStatus = flushExcessBinderRefs(session, addr, target);
     }
 
-    LOG_ALWAYS_FATAL_IF(std::numeric_limits<int32_t>::max() - sizeof(RpcWireHeader) -
-                                        sizeof(RpcWireReply) <
-                                reply.dataSize(),
+    uint32_t bodySize;
+    LOG_ALWAYS_FATAL_IF(__builtin_add_overflow(sizeof(RpcWireReply), reply.dataSize(), &bodySize),
                         "Too much data for reply %zu", reply.dataSize());
-
     RpcWireHeader cmdReply{
             .command = RPC_COMMAND_REPLY,
-            .bodySize = static_cast<uint32_t>(sizeof(RpcWireReply) + reply.dataSize()),
+            .bodySize = bodySize,
     };
     RpcWireReply rpcReply{
             .status = replyStatus,