[PATCH] D138891: [MachO] Prevent overflow on 32-bit platforms when calculating load command offsets

[A. Wilcox via Phabricator via llvm-commits]

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This prevents overflow which can lead to llvm-objdump incorrectly accepting a malformed MachO file.  This in turn caused the LLVM test suite to segfault on 32-bit Linux/musl platforms (since pointers are allocated in high memory on musl).

Fixes GitHub #56746.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138891

Files:
  llvm/lib/Object/MachOObjectFile.cpp


Index: llvm/lib/Object/MachOObjectFile.cpp
===================================================================
--- llvm/lib/Object/MachOObjectFile.cpp
+++ llvm/lib/Object/MachOObjectFile.cpp
@@ -191,7 +191,8 @@
 getLoadCommandInfo(const MachOObjectFile &Obj, const char *Ptr,
                    uint32_t LoadCommandIndex) {
   if (auto CmdOrErr = getStructOrErr<MachO::load_command>(Obj, Ptr)) {
-    if (CmdOrErr->cmdsize + Ptr > Obj.getData().end())
+    uint64_t Offset = Ptr - Obj.getData().begin();
+    if (CmdOrErr->cmdsize + Offset > Obj.getData().size())
       return malformedError("load command " + Twine(LoadCommandIndex) +
                             " extends past end of file");
     if (CmdOrErr->cmdsize < 8)


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