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don't call Memory::get without checking the pointer first #815

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Merged
merged 1 commit into from
Jul 1, 2019
Merged

don't call Memory::get without checking the pointer first #815

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10 changes: 7 additions & 3 deletions src/operator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -206,7 +206,7 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
// on read hardware this can easily happen. Thus for comparisons we require
// both pointers to be live.
if self.pointer_inbounds(left).is_ok() && self.pointer_inbounds(right).is_ok() {
// Two in-bounds pointers in different allocations are different.
// Two in-bounds (and hence live) pointers in different allocations are different.
false
} else {
return err!(InvalidPointerMath);
Expand Down Expand Up @@ -303,7 +303,9 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
map_to_primval(left.overflowing_offset(Size::from_bytes(right as u64), self)),

BitAnd if !signed => {
let ptr_base_align = self.memory().get(left.alloc_id)?.align.bytes();
let ptr_base_align = self.memory().get_size_and_align(left.alloc_id, AllocCheck::MaybeDead)
.expect("alloc info with MaybeDead cannot fail")
.1.bytes();
let base_mask = {
// FIXME: use `interpret::truncate`, once that takes a `Size` instead of a `Layout`.
let shift = 128 - self.memory().pointer_size().bits();
Expand Down Expand Up @@ -337,7 +339,9 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
Rem if !signed => {
// Doing modulo a divisor of the alignment is allowed.
// (Intuition: modulo a divisor leaks less information.)
let ptr_base_align = self.memory().get(left.alloc_id)?.align.bytes();
let ptr_base_align = self.memory().get_size_and_align(left.alloc_id, AllocCheck::MaybeDead)
.expect("alloc info with MaybeDead cannot fail")
.1.bytes();
let right = right as u64;
let ptr_size = self.memory().pointer_size();
if right == 1 {
Expand Down
32 changes: 20 additions & 12 deletions src/shims/foreign_items.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -252,9 +252,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
Align::from_bytes(align).unwrap(),
MiriMemoryKind::Rust.into()
);
// We just allocated this, the access cannot fail
this.memory_mut()
.get_mut(ptr.alloc_id)?
.write_repeat(tcx, ptr, 0, Size::from_bytes(size))?;
.get_mut(ptr.alloc_id).unwrap()
.write_repeat(tcx, ptr, 0, Size::from_bytes(size)).unwrap();
this.write_scalar(Scalar::Ptr(ptr), dest)?;
}
"__rust_dealloc" => {
Expand Down Expand Up @@ -494,15 +495,15 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
Align::from_bytes(1).unwrap(),
MiriMemoryKind::Env.into(),
);
{
let alloc = this.memory_mut().get_mut(value_copy.alloc_id)?;
alloc.write_bytes(tcx, value_copy, &value)?;
let trailing_zero_ptr = value_copy.offset(
Size::from_bytes(value.len() as u64),
tcx,
)?;
alloc.write_bytes(tcx, trailing_zero_ptr, &[0])?;
}
// We just allocated these, so the write cannot fail.
let alloc = this.memory_mut().get_mut(value_copy.alloc_id).unwrap();
alloc.write_bytes(tcx, value_copy, &value).unwrap();
let trailing_zero_ptr = value_copy.offset(
Size::from_bytes(value.len() as u64),
tcx,
).unwrap();
alloc.write_bytes(tcx, trailing_zero_ptr, &[0]).unwrap();

if let Some(var) = this.machine.env_vars.insert(
name.to_owned(),
value_copy,
Expand Down Expand Up @@ -839,7 +840,14 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
},
"GetSystemInfo" => {
let system_info = this.deref_operand(args[0])?;
let system_info_ptr = system_info.ptr.to_ptr()?;
let (system_info_ptr, align) = system_info.to_scalar_ptr_align();
let system_info_ptr = this.memory()
.check_ptr_access(
system_info_ptr,
system_info.layout.size,
align,
)?
.expect("cannot be a ZST");
// Initialize with `0`.
this.memory_mut().get_mut(system_info_ptr.alloc_id)?
.write_repeat(tcx, system_info_ptr, 0, system_info.layout.size)?;
Expand Down