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Rollup merge of rust-lang#63880 - RalfJung:miri-meta, r=oli-obk
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Validation: check raw wide pointer metadata

While I was at it, I also added a missing check for slices not to be too big.

r? @oli-obk
Fixes rust-lang/miri#918
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@Centril
Centril authored Aug 29, 2019
2 parents 57cc7f6 + 04580b6 commit c368379
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Showing 3 changed files with 177 additions and 101 deletions.
89 changes: 54 additions & 35 deletions src/librustc_mir/interpret/validity.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ use std::hash::Hash;

use super::{
GlobalAlloc, InterpResult,
OpTy, Machine, InterpCx, ValueVisitor, MPlaceTy,
Scalar, OpTy, Machine, InterpCx, ValueVisitor, MPlaceTy,
};

macro_rules! throw_validation_failure {
Expand Down Expand Up @@ -250,6 +250,47 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
self.path.truncate(path_len);
Ok(())
}

fn check_wide_ptr_meta(
&mut self,
meta: Option<Scalar<M::PointerTag>>,
pointee: TyLayout<'tcx>,
) -> InterpResult<'tcx> {
let tail = self.ecx.tcx.struct_tail_erasing_lifetimes(pointee.ty, self.ecx.param_env);
match tail.sty {
ty::Dynamic(..) => {
let vtable = meta.unwrap();
try_validation!(
self.ecx.memory.check_ptr_access(
vtable,
3*self.ecx.tcx.data_layout.pointer_size, // drop, size, align
self.ecx.tcx.data_layout.pointer_align.abi,
),
"dangling or unaligned vtable pointer in wide pointer or too small vtable",
self.path
);
try_validation!(self.ecx.read_drop_type_from_vtable(vtable),
"invalid drop fn in vtable", self.path);
try_validation!(self.ecx.read_size_and_align_from_vtable(vtable),
"invalid size or align in vtable", self.path);
// FIXME: More checks for the vtable.
}
ty::Slice(..) | ty::Str => {
let _len = try_validation!(meta.unwrap().to_usize(self.ecx),
"non-integer slice length in wide pointer", self.path);
// We do not check that `len * elem_size <= isize::MAX`:
// that is only required for references, and there it falls out of the
// "dereferencable" check performed by Stacked Borrows.
}
ty::Foreign(..) => {
// Unsized, but not wide.
}
_ =>
bug!("Unexpected unsized type tail: {:?}", tail),
}

Ok(())
}
}

impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
Expand Down Expand Up @@ -341,56 +382,34 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
}
}
ty::RawPtr(..) => {
// Check pointer part.
if self.ref_tracking_for_consts.is_some() {
// Integers/floats in CTFE: For consistency with integers, we do not
// accept undef.
let _ptr = try_validation!(value.to_scalar_ptr(),
"undefined address in raw pointer", self.path);
let _meta = try_validation!(value.to_meta(),
"uninitialized data in raw fat pointer metadata", self.path);
} else {
// Remain consistent with `usize`: Accept anything.
}

// Check metadata.
let meta = try_validation!(value.to_meta(),
"uninitialized data in wide pointer metadata", self.path);
let layout = self.ecx.layout_of(value.layout.ty.builtin_deref(true).unwrap().ty)?;
if layout.is_unsized() {
self.check_wide_ptr_meta(meta, layout)?;
}
}
_ if ty.is_box() || ty.is_region_ptr() => {
// Handle fat pointers.
// Handle wide pointers.
// Check metadata early, for better diagnostics
let ptr = try_validation!(value.to_scalar_ptr(),
"undefined address in pointer", self.path);
let meta = try_validation!(value.to_meta(),
"uninitialized data in fat pointer metadata", self.path);
"uninitialized data in wide pointer metadata", self.path);
let layout = self.ecx.layout_of(value.layout.ty.builtin_deref(true).unwrap().ty)?;
if layout.is_unsized() {
let tail = self.ecx.tcx.struct_tail_erasing_lifetimes(layout.ty,
self.ecx.param_env);
match tail.sty {
ty::Dynamic(..) => {
let vtable = meta.unwrap();
try_validation!(
self.ecx.memory.check_ptr_access(
vtable,
3*self.ecx.tcx.data_layout.pointer_size, // drop, size, align
self.ecx.tcx.data_layout.pointer_align.abi,
),
"dangling or unaligned vtable pointer or too small vtable",
self.path
);
try_validation!(self.ecx.read_drop_type_from_vtable(vtable),
"invalid drop fn in vtable", self.path);
try_validation!(self.ecx.read_size_and_align_from_vtable(vtable),
"invalid size or align in vtable", self.path);
// FIXME: More checks for the vtable.
}
ty::Slice(..) | ty::Str => {
try_validation!(meta.unwrap().to_usize(self.ecx),
"non-integer slice length in fat pointer", self.path);
}
ty::Foreign(..) => {
// Unsized, but not fat.
}
_ =>
bug!("Unexpected unsized type tail: {:?}", tail),
}
self.check_wide_ptr_meta(meta, layout)?;
}
// Make sure this is dereferencable and all.
let (size, align) = self.ecx.size_and_align_of(meta, layout)?
Expand Down
73 changes: 49 additions & 24 deletions .../ui/consts/const-eval/union-ub-fat-ptr.rs → src/test/ui/consts/const-eval/ub-wide-ptr.rs
View file
Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
// ignore-tidy-linelength
#![allow(unused)]
#![allow(const_err)] // make sure we cannot allow away the errors tested here

Expand Down Expand Up @@ -28,7 +29,9 @@ struct BadSliceRepr {
union SliceTransmute {
repr: SliceRepr,
bad: BadSliceRepr,
addr: usize,
slice: &'static [u8],
raw_slice: *const [u8],
str: &'static str,
my_str: &'static MyStr,
my_slice: &'static MySliceBool,
Expand Down Expand Up @@ -59,7 +62,9 @@ union DynTransmute {
repr: DynRepr,
repr2: DynRepr2,
bad: BadDynRepr,
addr: usize,
rust: &'static dyn Trait,
raw_rust: *const dyn Trait,
}

trait Trait {}
Expand All @@ -72,39 +77,37 @@ struct MyStr(str);
struct MySlice<T: ?Sized>(bool, T);
type MySliceBool = MySlice<[bool]>;

// # str
// OK
const A: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.str};
const STR_VALID: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.str};
// bad str
const B: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.str};
const STR_TOO_LONG: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.str};
//~^ ERROR it is undefined behavior to use this value
// bad str
const C: &str = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.str};
const STR_LENGTH_PTR: &str = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.str};
//~^ ERROR it is undefined behavior to use this value
// bad str in user-defined unsized type
const C2: &MyStr = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.my_str};
const MY_STR_LENGTH_PTR: &MyStr = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.my_str};
//~^ ERROR it is undefined behavior to use this value

// OK
const A2: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.slice};
// bad slice
const B2: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.slice};
// invalid UTF-8
const J1: &str = unsafe { SliceTransmute { slice: &[0xFF] }.str };
//~^ ERROR it is undefined behavior to use this value
// bad slice
const C3: &[u8] = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.slice};
// invalid UTF-8 in user-defined str-like
const J2: &MyStr = unsafe { SliceTransmute { slice: &[0xFF] }.my_str };
//~^ ERROR it is undefined behavior to use this value

// bad trait object
const D: &dyn Trait = unsafe { DynTransmute { repr: DynRepr { ptr: &92, vtable: &3 } }.rust};
//~^ ERROR it is undefined behavior to use this value
// bad trait object
const E: &dyn Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.rust};
// # slice
// OK
const SLICE_VALID: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.slice};
// bad slice: length uninit
const SLICE_LENGTH_UNINIT: &[u8] = unsafe { SliceTransmute { addr: 42 }.slice};
//~^ ERROR it is undefined behavior to use this value
// bad trait object
const F: &dyn Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 3 } }.rust};
// bad slice: length too big
const SLICE_TOO_LONG: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.slice};
//~^ ERROR it is undefined behavior to use this value

// bad data *inside* the trait object
const G: &dyn Trait = &unsafe { BoolTransmute { val: 3 }.bl };
// bad slice: length not an int
const SLICE_LENGTH_PTR: &[u8] = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.slice};
//~^ ERROR it is undefined behavior to use this value

// bad data *inside* the slice
Expand All @@ -120,12 +123,34 @@ const I2: &MySliceBool = &MySlice(unsafe { BoolTransmute { val: 3 }.bl }, [false
const I3: &MySliceBool = &MySlice(true, [unsafe { BoolTransmute { val: 3 }.bl }]);
//~^ ERROR it is undefined behavior to use this value

// invalid UTF-8
const J1: &str = unsafe { SliceTransmute { slice: &[0xFF] }.str };
// # raw slice
const RAW_SLICE_VALID: *const [u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.raw_slice}; // ok
const RAW_SLICE_TOO_LONG: *const [u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.raw_slice}; // ok because raw
const RAW_SLICE_MUCH_TOO_LONG: *const [u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: usize::max_value() } }.raw_slice}; // ok because raw
const RAW_SLICE_LENGTH_UNINIT: *const [u8] = unsafe { SliceTransmute { addr: 42 }.raw_slice};
//~^ ERROR it is undefined behavior to use this value
// invalid UTF-8 in user-defined str-like
const J2: &MyStr = unsafe { SliceTransmute { slice: &[0xFF] }.my_str };

// # trait object
// bad trait object
const D: &dyn Trait = unsafe { DynTransmute { repr: DynRepr { ptr: &92, vtable: &3 } }.rust};
//~^ ERROR it is undefined behavior to use this value
// bad trait object
const E: &dyn Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.rust};
//~^ ERROR it is undefined behavior to use this value
// bad trait object
const F: &dyn Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 3 } }.rust};
//~^ ERROR it is undefined behavior to use this value

// bad data *inside* the trait object
const G: &dyn Trait = &unsafe { BoolTransmute { val: 3 }.bl };
//~^ ERROR it is undefined behavior to use this value

// # raw trait object
const RAW_TRAIT_OBJ_VTABLE_NULL: *const dyn Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 0 } }.rust};
//~^ ERROR it is undefined behavior to use this value
const RAW_TRAIT_OBJ_VTABLE_INVALID: *const dyn Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.raw_rust};
//~^ ERROR it is undefined behavior to use this value
const RAW_TRAIT_OBJ_CONTENT_INVALID: *const dyn Trait = &unsafe { BoolTransmute { val: 3 }.bl } as *const _; // ok because raw

fn main() {
}
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