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Asan use-after-scope: don't poison allocas if there were untraced lifetime intrinsics in the function (PR41481) 

If there are any intrinsics that cannot be traced back to an alloca, we
might have missed the start of a variable's scope, leading to false
error reports if the variable is poisoned at function entry. Instead, if
there are some intrinsics that can't be traced, fail safe and don't
poison the variables in that function.

Differential revision: https://reviews.llvm.org/D60686

llvm-svn: 358478
This commit is contained in:
Hans Wennborg 2019-04-16 07:54:20 +00:00
parent 376230c9ef
commit 6ae05777b8
2 changed files with 50 additions and 1 deletions
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15
llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
View File

@ -884,6 +884,7 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
};
SmallVector<AllocaPoisonCall, 8> DynamicAllocaPoisonCallVec;
SmallVector<AllocaPoisonCall, 8> StaticAllocaPoisonCallVec;
bool HasUntracedLifetimeIntrinsic = false;
SmallVector<AllocaInst *, 1> DynamicAllocaVec;
SmallVector<IntrinsicInst *, 1> StackRestoreVec;
@ -918,6 +919,14 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
initializeCallbacks(*F.getParent());
if (HasUntracedLifetimeIntrinsic) {
// If there are lifetime intrinsics which couldn't be traced back to an
// alloca, we may not know exactly when a variable enters scope, and
// therefore should "fail safe" by not poisoning them.
StaticAllocaPoisonCallVec.clear();
DynamicAllocaPoisonCallVec.clear();
}
processDynamicAllocas();
processStaticAllocas();
@ -1040,8 +1049,12 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
// Find alloca instruction that corresponds to llvm.lifetime argument.
AllocaInst *AI =
llvm::findAllocaForValue(II.getArgOperand(1), AllocaForValue);
if (!AI) {
HasUntracedLifetimeIntrinsic = true;
return;
}
// We're interested only in allocas we can handle.
if (!AI || !ASan.isInterestingAlloca(*AI))
if (!ASan.isInterestingAlloca(*AI))
return;
bool DoPoison = (ID == Intrinsic::lifetime_end);
AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};

36
llvm/test/Instrumentation/AddressSanitizer/stack-poisoning-and-lifetime.ll
View File

@ -209,6 +209,42 @@ entry:
; CHECK: ret void
}
declare void @foo(i32*)
define void @PR41481(i1 %b) sanitize_address {
; CHECK-LABEL: @PR41481
entry:
%p1 = alloca i32
%p2 = alloca i32
%q1 = bitcast i32* %p1 to i8*
%q2 = bitcast i32* %p2 to i8*
br label %bb1
; Since we cannot account for all lifetime intrinsics in this function, we
; might have missed a lifetime.start one and therefore shouldn't poison the
; allocas at function entry.
; ENTRY: store i64 -935356719533264399
; ENTRY-UAS: store i64 -935356719533264399
bb1:
%p = select i1 %b, i32* %p1, i32* %p2
%q = select i1 %b, i8* %q1, i8* %q2
call void @llvm.lifetime.start.p0i8(i64 4, i8* %q)
call void @foo(i32* %p)
br i1 %b, label %bb2, label %bb3
bb2:
call void @llvm.lifetime.end.p0i8(i64 4, i8* %q1)
br label %end
bb3:
call void @llvm.lifetime.end.p0i8(i64 4, i8* %q2)
br label %end
end:
ret void
}
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)