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[clang][CodeGen][UBSan] VLA size checking for unsigned integer parameter 

The code generation for the UBSan VLA size check was qualified by a con-
dition that the parameter must be a signed integer, however the C spec
does not make any distinction that only signed integer parameters can be
used to declare a VLA, only qualifying that it must be greater than zero
if it is not a constant.

Reviewed By: rjmccall

Differential Revision: https://reviews.llvm.org/D116048
This commit is contained in:
Adam Magier 2021-12-17 00:56:43 +01:00
parent b7f298f174
commit b2715660ed
2 changed files with 27 additions and 12 deletions
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28
clang/lib/CodeGen/CodeGenFunction.cpp
View File

@ -2247,32 +2247,36 @@ void CodeGenFunction::EmitVariablyModifiedType(QualType type) {
// Unknown size indication requires no size computation.
// Otherwise, evaluate and record it.
if (const Expr *size = vat->getSizeExpr()) {
if (const Expr *sizeExpr = vat->getSizeExpr()) {
// It's possible that we might have emitted this already,
// e.g. with a typedef and a pointer to it.
llvm::Value *&entry = VLASizeMap[size];
llvm::Value *&entry = VLASizeMap[sizeExpr];
if (!entry) {
llvm::Value *Size = EmitScalarExpr(size);
llvm::Value *size = EmitScalarExpr(sizeExpr);
// C11 6.7.6.2p5:
// If the size is an expression that is not an integer constant
// expression [...] each time it is evaluated it shall have a value
// greater than zero.
if (SanOpts.has(SanitizerKind::VLABound) &&
size->getType()->isSignedIntegerType()) {
if (SanOpts.has(SanitizerKind::VLABound)) {
SanitizerScope SanScope(this);
llvm::Value *Zero = llvm::Constant::getNullValue(Size->getType());
llvm::Value *Zero = llvm::Constant::getNullValue(size->getType());
clang::QualType SEType = sizeExpr->getType();
llvm::Value *CheckCondition =
SEType->isSignedIntegerType()
? Builder.CreateICmpSGT(size, Zero)
: Builder.CreateICmpUGT(size, Zero);
llvm::Constant *StaticArgs[] = {
EmitCheckSourceLocation(size->getBeginLoc()),
EmitCheckTypeDescriptor(size->getType())};
EmitCheck(std::make_pair(Builder.CreateICmpSGT(Size, Zero),
SanitizerKind::VLABound),
SanitizerHandler::VLABoundNotPositive, StaticArgs, Size);
EmitCheckSourceLocation(sizeExpr->getBeginLoc()),
EmitCheckTypeDescriptor(SEType)};
EmitCheck(std::make_pair(CheckCondition, SanitizerKind::VLABound),
SanitizerHandler::VLABoundNotPositive, StaticArgs, size);
}
// Always zexting here would be wrong if it weren't
// undefined behavior to have a negative bound.
entry = Builder.CreateIntCast(Size, SizeTy, /*signed*/ false);
// FIXME: What about when size's type is larger than size_t?
entry = Builder.CreateIntCast(size, SizeTy, /*signed*/ false);
}
}
type = vat->getElementType();

11
clang/test/CodeGen/catch-undef-behavior.c
View File

@ -17,6 +17,7 @@
// CHECK-UBSAN: @[[LINE_700:.*]] = {{.*}}, i32 700, i32 14 {{.*}} @[[STRUCT_S]], i8 2, i8 3 }
// CHECK-UBSAN: @[[LINE_800:.*]] = {{.*}}, i32 800, i32 12 {{.*}} @{{.*}} }
// CHECK-UBSAN: @[[LINE_900:.*]] = {{.*}}, i32 900, i32 11 {{.*}} @{{.*}} }
// CHECK-UBSAN: @[[LINE_1000:.*]] = {{.*}}, i32 1000, i32 11 {{.*}} @{{.*}} }
// CHECK-UBSAN: @[[FP16:.*]] = private unnamed_addr constant { i16, i16, [9 x i8] } { i16 1, i16 16, [9 x i8] c"'__fp16'\00" }
// CHECK-UBSAN: @[[LINE_1200:.*]] = {{.*}}, i32 1200, i32 10 {{.*}} @{{.*}} }
// CHECK-UBSAN: @[[LINE_1300:.*]] = {{.*}}, i32 1300, i32 10 {{.*}} @{{.*}} }
@ -186,6 +187,16 @@ void vla_bound(int n) {
int arr[n * 3];
}
// CHECK-UBSAN-LABEL: @vla_bound_unsigned
void vla_bound_unsigned(unsigned int n) {
// CHECK-UBSAN: icmp ugt i32 %[[PARAM:.*]], 0
//
// CHECK-UBSAN: %[[ARG:.*]] = zext i32 %[[PARAM]] to i64
// CHECK-UBSAN-NEXT: call void @__ubsan_handle_vla_bound_not_positive(i8* bitcast ({{.*}} @[[LINE_1000]] to i8*), i64 %[[ARG]])
#line 1000
int arr[n * 3];
}
// CHECK-UBSAN-LABEL: @int_float_no_overflow
float int_float_no_overflow(__int128 n) {
// CHECK-UBSAN-NOT: call void @__ubsan_handle