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[BPF] fix a use after free bug

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Commit fff2721286e1 ("[BPF] Fix CO-RE bugs with bitfields")
fixed CO-RE handling bitfield issues. But the implementation
introduced a use after free bug. The "Base" of the intrinsic
might be freed so later on accessing the Type of "Base"
might access the freed memory. The failed test case,
  CodeGen/BPF/CORE/offset-reloc-middle-chain.ll
is exactly used to test such a case.

Similarly to previous attempt to remember Metadata etc,
remember "Base" pointee Alignment in advance to avoid
such use after free bug.
This commit is contained in:
Yonghong Song 2019-11-04 22:12:52 -08:00
parent 74c9f1897a
commit 4e15497cad
1 changed files with 8 additions and 2 deletions
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10
lib/Target/BPF/BPFAbstractMemberAccess.cpp
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@ -117,6 +117,7 @@ public:
struct CallInfo {
uint32_t Kind;
uint32_t AccessIndex;
uint32_t RecordAlignment;
MDNode *Metadata;
Value *Base;
};
@ -246,6 +247,8 @@ bool BPFAbstractMemberAccess::IsPreserveDIAccessIndexCall(const CallInst *Call,
report_fatal_error("Missing metadata for llvm.preserve.array.access.index intrinsic");
CInfo.AccessIndex = getConstant(Call->getArgOperand(2));
CInfo.Base = Call->getArgOperand(0);
CInfo.RecordAlignment =
DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
return true;
}
if (GV->getName().startswith("llvm.preserve.union.access.index")) {
@ -255,6 +258,8 @@ bool BPFAbstractMemberAccess::IsPreserveDIAccessIndexCall(const CallInst *Call,
report_fatal_error("Missing metadata for llvm.preserve.union.access.index intrinsic");
CInfo.AccessIndex = getConstant(Call->getArgOperand(1));
CInfo.Base = Call->getArgOperand(0);
CInfo.RecordAlignment =
DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
return true;
}
if (GV->getName().startswith("llvm.preserve.struct.access.index")) {
@ -264,6 +269,8 @@ bool BPFAbstractMemberAccess::IsPreserveDIAccessIndexCall(const CallInst *Call,
report_fatal_error("Missing metadata for llvm.preserve.struct.access.index intrinsic");
CInfo.AccessIndex = getConstant(Call->getArgOperand(2));
CInfo.Base = Call->getArgOperand(0);
CInfo.RecordAlignment =
DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
return true;
}
if (GV->getName().startswith("llvm.bpf.preserve.field.info")) {
@ -815,8 +822,7 @@ Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call,
AccessKey += ":" + std::to_string(AccessIndex);
MDNode *MDN = CInfo.Metadata;
uint32_t RecordAlignment =
DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
uint32_t RecordAlignment = CInfo.RecordAlignment;
// At this stage, it cannot be pointer type.
auto *CTy = cast<DICompositeType>(stripQualifiers(cast<DIType>(MDN)));
PatchImm = GetFieldInfo(InfoKind, CTy, AccessIndex, PatchImm,