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CFI: Fix SIGILL reached via trait objects
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Fix #106547 by transforming the concrete self into a reference to a
trait object before emitting type metadata identifiers for trait
methods.
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rcvalle committed May 9, 2023
1 parent eac3558 commit 7c7b22e
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Showing 10 changed files with 247 additions and 28 deletions.
4 changes: 2 additions & 2 deletions compiler/rustc_codegen_llvm/src/callee.rs
Original file line number Diff line number Diff line change
Expand Up @@ -94,11 +94,11 @@ pub fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) ->
// LLVM will prefix the name with `__imp_`. Ideally, we'd like the
// existing logic below to set the Storage Class, but it has an
// exemption for MinGW for backwards compatability.
let llfn = cx.declare_fn(&common::i686_decorated_name(&dllimport, common::is_mingw_gnu_toolchain(&tcx.sess.target), true), fn_abi);
let llfn = cx.declare_fn(&common::i686_decorated_name(&dllimport, common::is_mingw_gnu_toolchain(&tcx.sess.target), true), fn_abi, Some(instance));
unsafe { llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport); }
llfn
} else {
cx.declare_fn(sym, fn_abi)
cx.declare_fn(sym, fn_abi, Some(instance))
};
debug!("get_fn: not casting pointer!");

Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -207,6 +207,7 @@ fn declare_unused_fn<'tcx>(cx: &CodegenCx<'_, 'tcx>, def_id: DefId) -> Instance<
)),
ty::List::empty(),
),
None,
);

llvm::set_linkage(llfn, llvm::Linkage::PrivateLinkage);
Expand Down
64 changes: 47 additions & 17 deletions compiler/rustc_codegen_llvm/src/declare.rs
Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,11 @@ use crate::llvm::AttributePlace::Function;
use crate::type_::Type;
use crate::value::Value;
use rustc_codegen_ssa::traits::TypeMembershipMethods;
use rustc_middle::ty::Ty;
use rustc_symbol_mangling::typeid::{kcfi_typeid_for_fnabi, typeid_for_fnabi, TypeIdOptions};
use rustc_middle::ty::{Instance, Ty};
use rustc_symbol_mangling::typeid::{
kcfi_typeid_for_fnabi, kcfi_typeid_for_instance, typeid_for_fnabi, typeid_for_instance,
TypeIdOptions,
};
use smallvec::SmallVec;

/// Declare a function.
Expand Down Expand Up @@ -116,7 +119,12 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
///
/// If there’s a value with the same name already declared, the function will
/// update the declaration and return existing Value instead.
pub fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> &'ll Value {
pub fn declare_fn(
&self,
name: &str,
fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
instance: Option<Instance<'tcx>>,
) -> &'ll Value {
debug!("declare_rust_fn(name={:?}, fn_abi={:?})", name, fn_abi);

// Function addresses in Rust are never significant, allowing functions to
Expand All @@ -132,18 +140,35 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
fn_abi.apply_attrs_llfn(self, llfn);

if self.tcx.sess.is_sanitizer_cfi_enabled() {
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::empty());
self.set_type_metadata(llfn, typeid);
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::GENERALIZE_POINTERS);
self.add_type_metadata(llfn, typeid);
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::NORMALIZE_INTEGERS);
self.add_type_metadata(llfn, typeid);
let typeid = typeid_for_fnabi(
self.tcx,
fn_abi,
TypeIdOptions::GENERALIZE_POINTERS | TypeIdOptions::NORMALIZE_INTEGERS,
);
self.add_type_metadata(llfn, typeid);
if let Some(instance) = instance {
let typeid = typeid_for_instance(self.tcx, &instance, TypeIdOptions::empty());
self.set_type_metadata(llfn, typeid);
let typeid =
typeid_for_instance(self.tcx, &instance, TypeIdOptions::GENERALIZE_POINTERS);
self.add_type_metadata(llfn, typeid);
let typeid =
typeid_for_instance(self.tcx, &instance, TypeIdOptions::NORMALIZE_INTEGERS);
self.add_type_metadata(llfn, typeid);
let typeid = typeid_for_instance(
self.tcx,
&instance,
TypeIdOptions::GENERALIZE_POINTERS | TypeIdOptions::NORMALIZE_INTEGERS,
);
self.add_type_metadata(llfn, typeid);
} else {
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::empty());
self.set_type_metadata(llfn, typeid);
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::GENERALIZE_POINTERS);
self.add_type_metadata(llfn, typeid);
let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::NORMALIZE_INTEGERS);
self.add_type_metadata(llfn, typeid);
let typeid = typeid_for_fnabi(
self.tcx,
fn_abi,
TypeIdOptions::GENERALIZE_POINTERS | TypeIdOptions::NORMALIZE_INTEGERS,
);
self.add_type_metadata(llfn, typeid);
}
}

if self.tcx.sess.is_sanitizer_kcfi_enabled() {
Expand All @@ -156,8 +181,13 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
options.insert(TypeIdOptions::NORMALIZE_INTEGERS);
}

let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi, options);
self.set_kcfi_type_metadata(llfn, kcfi_typeid);
if let Some(instance) = instance {
let kcfi_typeid = kcfi_typeid_for_instance(self.tcx, &instance, options);
self.set_kcfi_type_metadata(llfn, kcfi_typeid);
} else {
let kcfi_typeid = kcfi_typeid_for_fnabi(self.tcx, fn_abi, options);
self.set_kcfi_type_metadata(llfn, kcfi_typeid);
}
}

llfn
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_llvm/src/intrinsic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -772,7 +772,7 @@ fn gen_fn<'ll, 'tcx>(
) -> (&'ll Type, &'ll Value) {
let fn_abi = cx.fn_abi_of_fn_ptr(rust_fn_sig, ty::List::empty());
let llty = fn_abi.llvm_type(cx);
let llfn = cx.declare_fn(name, fn_abi);
let llfn = cx.declare_fn(name, fn_abi, None);
cx.set_frame_pointer_type(llfn);
cx.apply_target_cpu_attr(llfn);
// FIXME(eddyb) find a nicer way to do this.
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_llvm/src/mono_item.rs
Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ impl<'tcx> PreDefineMethods<'tcx> for CodegenCx<'_, 'tcx> {
assert!(!instance.substs.has_infer());

let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty());
let lldecl = self.declare_fn(symbol_name, fn_abi);
let lldecl = self.declare_fn(symbol_name, fn_abi, Some(instance));
unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
base::set_link_section(lldecl, attrs);
Expand Down
24 changes: 23 additions & 1 deletion compiler/rustc_symbol_mangling/src/typeid.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
/// For more information about LLVM CFI and cross-language LLVM CFI support for the Rust compiler,
/// see design document in the tracking issue #89653.
use bitflags::bitflags;
use rustc_middle::ty::{FnSig, Ty, TyCtxt};
use rustc_middle::ty::{FnSig, Instance, Ty, TyCtxt};
use rustc_target::abi::call::FnAbi;
use std::hash::Hasher;
use twox_hash::XxHash64;
Expand Down Expand Up @@ -38,6 +38,15 @@ pub fn typeid_for_fnsig<'tcx>(
typeid_itanium_cxx_abi::typeid_for_fnsig(tcx, fn_sig, options)
}

/// Returns a type metadata identifier for the specified Instance.
pub fn typeid_for_instance<'tcx>(
tcx: TyCtxt<'tcx>,
instance: &Instance<'tcx>,
options: TypeIdOptions,
) -> String {
typeid_itanium_cxx_abi::typeid_for_instance(tcx, instance, options)
}

/// Returns a KCFI type metadata identifier for the specified FnAbi.
pub fn kcfi_typeid_for_fnabi<'tcx>(
tcx: TyCtxt<'tcx>,
Expand All @@ -63,3 +72,16 @@ pub fn kcfi_typeid_for_fnsig<'tcx>(
hash.write(typeid_itanium_cxx_abi::typeid_for_fnsig(tcx, fn_sig, options).as_bytes());
hash.finish() as u32
}

/// Returns a KCFI type metadata identifier for the specified Instance.
pub fn kcfi_typeid_for_instance<'tcx>(
tcx: TyCtxt<'tcx>,
instance: &Instance<'tcx>,
options: TypeIdOptions,
) -> u32 {
// A KCFI type metadata identifier is a 32-bit constant produced by taking the lower half of the
// xxHash64 of the type metadata identifier. (See llvm/llvm-project@cff5bef.)
let mut hash: XxHash64 = Default::default();
hash.write(typeid_itanium_cxx_abi::typeid_for_instance(tcx, instance, options).as_bytes());
hash.finish() as u32
}
Original file line number Diff line number Diff line change
Expand Up @@ -14,8 +14,8 @@ use rustc_errors::DiagnosticMessage;
use rustc_hir as hir;
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
use rustc_middle::ty::{
self, Const, ExistentialPredicate, FloatTy, FnSig, IntTy, List, Region, RegionKind, TermKind,
Ty, TyCtxt, UintTy,
self, Const, ExistentialPredicate, FloatTy, FnSig, Instance, IntTy, List, Region, RegionKind,
TermKind, Ty, TyCtxt, UintTy,
};
use rustc_span::def_id::DefId;
use rustc_span::sym;
Expand Down Expand Up @@ -1010,3 +1010,56 @@ pub fn typeid_for_fnsig<'tcx>(

typeid
}

/// Returns a type metadata identifier for the specified Instance using the Itanium C++ ABI with
/// vendor extended type qualifiers and types for Rust types that are not used at the FFI boundary.
pub fn typeid_for_instance<'tcx>(
tcx: TyCtxt<'tcx>,
instance: &Instance<'tcx>,
options: TypeIdOptions,
) -> String {
let fn_abi = tcx
.fn_abi_of_instance(tcx.param_env(instance.def_id()).and((*instance, ty::List::empty())))
.unwrap_or_else(|instance| {
bug!("typeid_for_instance: couldn't get fn_abi of instance {:?}", instance)
});

// If this instance is a method and self is a reference, get the impl it belongs to
let impl_def_id = tcx.impl_of_method(instance.def_id());
if impl_def_id.is_some() && !fn_abi.args.is_empty() && fn_abi.args[0].layout.ty.is_ref() {
// If this impl is not an inherent impl, get the trait it implements
if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id.unwrap()) {
// Transform the concrete self into a reference to a trait object
let existential_predicate = trait_ref.map_bound(|trait_ref| {
ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef::erase_self_ty(
tcx, trait_ref,
))
});
let existential_predicates = tcx.mk_poly_existential_predicates(&[ty::Binder::dummy(
existential_predicate.skip_binder(),
)]);
// Is the concrete self mutable?
let self_ty = if fn_abi.args[0].layout.ty.is_mutable_ptr() {
tcx.mk_mut_ref(
tcx.lifetimes.re_erased,
tcx.mk_dynamic(existential_predicates, tcx.lifetimes.re_erased, ty::Dyn),
)
} else {
tcx.mk_imm_ref(
tcx.lifetimes.re_erased,
tcx.mk_dynamic(existential_predicates, tcx.lifetimes.re_erased, ty::Dyn),
)
};

// Replace the concrete self in an fn_abi clone by the reference to a trait object
let mut fn_abi = fn_abi.clone();
// HACK(rcvalle): It is okay to not replace or update the entire ArgAbi here because the
// other fields are never used.
fn_abi.args[0].layout.ty = self_ty;

return typeid_for_fnabi(tcx, &fn_abi, options);
}
}

typeid_for_fnabi(tcx, &fn_abi, options)
}
8 changes: 4 additions & 4 deletions compiler/rustc_target/src/abi/call/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ mod x86;
mod x86_64;
mod x86_win64;

#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
#[derive(Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub enum PassMode {
/// Ignore the argument.
///
Expand Down Expand Up @@ -211,7 +211,7 @@ impl Uniform {
}
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
#[derive(Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct CastTarget {
pub prefix: [Option<Reg>; 8],
pub rest: Uniform,
Expand Down Expand Up @@ -458,7 +458,7 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {

/// Information about how to pass an argument to,
/// or return a value from, a function, under some ABI.
#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
#[derive(Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct ArgAbi<'a, Ty> {
pub layout: TyAndLayout<'a, Ty>,
pub mode: PassMode,
Expand Down Expand Up @@ -605,7 +605,7 @@ pub enum Conv {
///
/// I will do my best to describe this structure, but these
/// comments are reverse-engineered and may be inaccurate. -NDM
#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
#[derive(Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct FnAbi<'a, Ty> {
/// The LLVM types of each argument.
pub args: Box<[ArgAbi<'a, Ty>]>,
Expand Down
44 changes: 44 additions & 0 deletions tests/codegen/sanitizer-cfi-emit-type-metadata-trait-objects.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,44 @@
// Verifies that type metadata identifiers for trait objects are emitted correctly.
//
// needs-sanitizer-cfi
// compile-flags: -Clto -Cno-prepopulate-passes -Ctarget-feature=-crt-static -Zsanitizer=cfi

#![crate_type="lib"]

trait Trait1 {
fn foo(&self);
}

struct Type1;

impl Trait1 for Type1 {
fn foo(&self) {
}
}

pub fn foo() {
let a = Type1;
a.foo();
// CHECK-LABEL: define{{.*}}foo{{.*}}!type !{{[0-9]+}}
// CHECK: call <sanitizer_cfi_emit_type_metadata_trait_objects::Type1 as sanitizer_cfi_emit_type_metadata_trait_objects::Trait1>::foo
}

pub fn bar() {
let a = Type1;
let b = &a as &dyn Trait1;
b.foo();
// CHECK-LABEL: define{{.*}}bar{{.*}}!type !{{[0-9]+}}
// CHECK: call i1 @llvm.type.test({{i8\*|ptr}} {{%f|%0|%1}}, metadata !"[[TYPE1:[[:print:]]+]]")
}

pub fn baz() {
let a = Type1;
let b = &a as &dyn Trait1;
a.foo();
b.foo();
// CHECK-LABEL: define{{.*}}baz{{.*}}!type !{{[0-9]+}}
// CHECK: call <sanitizer_cfi_emit_type_metadata_trait_objects::Type1 as sanitizer_cfi_emit_type_metadata_trait_objects::Trait1>::foo
// CHECK: call i1 @llvm.type.test({{i8\*|ptr}} {{%f|%0|%1}}, metadata !"[[TYPE1:[[:print:]]+]]")
}

// CHECK: !{{[0-9]+}} = !{i64 0, !"[[TYPE1]]"}
69 changes: 69 additions & 0 deletions tests/codegen/sanitizer-kcfi-emit-type-metadata-trait-objects.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,69 @@
// Verifies that type metadata identifiers for trait objects are emitted correctly.
//
// revisions: aarch64 x86_64
// [aarch64] compile-flags: --target aarch64-unknown-none
// [aarch64] needs-llvm-components: aarch64
// [x86_64] compile-flags: --target x86_64-unknown-none
// [x86_64] needs-llvm-components:
// compile-flags: -Cno-prepopulate-passes -Zsanitizer=kcfi -Copt-level=0

#![crate_type="lib"]
#![feature(arbitrary_self_types, no_core, lang_items)]
#![no_core]

#[lang="sized"]
trait Sized { }
#[lang="copy"]
trait Copy { }
#[lang="receiver"]
trait Receiver { }
#[lang="dispatch_from_dyn"]
trait DispatchFromDyn<T> { }
impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<&'a U> for &'a T {}
#[lang = "unsize"]
trait Unsize<T: ?Sized> { }
#[lang = "coerce_unsized"]
pub trait CoerceUnsized<T: ?Sized> { }
impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
#[lang="freeze"]
trait Freeze { }
#[lang="drop_in_place"]
fn drop_in_place_fn<T>() { }

trait Trait1 {
fn foo(&self);
}

struct Type1;

impl Trait1 for Type1 {
fn foo(&self) {
}
}

pub fn foo() {
let a = Type1;
a.foo();
// CHECK-LABEL: define{{.*}}foo{{.*}}!{{<unknown kind #36>|kcfi_type}} !{{[0-9]+}}
// CHECK: call <sanitizer_kcfi_emit_type_metadata_trait_objects::Type1 as sanitizer_kcfi_emit_type_metadata_trait_objects::Trait1>::foo
}

pub fn bar() {
let a = Type1;
let b = &a as &dyn Trait1;
b.foo();
// CHECK-LABEL: define{{.*}}bar{{.*}}!{{<unknown kind #36>|kcfi_type}} !{{[0-9]+}}
// CHECK: call void %0({{\{\}\*|ptr}} align 1 {{%b\.0|%_1}}){{.*}}[ "kcfi"(i32 [[TYPE1:[[:print:]]+]]) ]
}

pub fn baz() {
let a = Type1;
let b = &a as &dyn Trait1;
a.foo();
b.foo();
// CHECK-LABEL: define{{.*}}baz{{.*}}!{{<unknown kind #36>|kcfi_type}} !{{[0-9]+}}
// CHECK: call <sanitizer_kcfi_emit_type_metadata_trait_objects::Type1 as sanitizer_kcfi_emit_type_metadata_trait_objects::Trait1>::foo
// CHECK: call void %0({{\{\}\*|ptr}} align 1 {{%b\.0|%_1}}){{.*}}[ "kcfi"(i32 [[TYPE1:[[:print:]]+]]) ]
}

// CHECK: !{{[0-9]+}} = !{i32 [[TYPE1]]}

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