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fix slice::check_range aliasing problems

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This commit is contained in:
Ralf Jung 2020-09-13 12:14:59 +02:00
parent d888725fba
commit c528d24196
7 changed files with 85 additions and 86 deletions
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6
library/alloc/src/collections/vec_deque.rs
View File

@ -1089,11 +1089,7 @@ impl<T> VecDeque<T> {
where
R: RangeBounds<usize>,
{
// SAFETY: This buffer is only used to check the range. It might be partially
// uninitialized, but `check_range` needs a contiguous slice.
// https://github.com/rust-lang/rust/pull/75207#discussion_r471193682
let buffer = unsafe { slice::from_raw_parts(self.ptr(), self.len()) };
let Range { start, end } = buffer.check_range(range);
let Range { start, end } = slice::check_range(self.len(), range);
let tail = self.wrap_add(self.tail, start);
let head = self.wrap_add(self.tail, end);
(tail, head)

2
library/alloc/src/slice.rs
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@ -91,6 +91,8 @@ use crate::borrow::ToOwned;
use crate::boxed::Box;
use crate::vec::Vec;
#[unstable(feature = "slice_check_range", issue = "76393")]
pub use core::slice::check_range;
#[unstable(feature = "array_chunks", issue = "74985")]
pub use core::slice::ArrayChunks;
#[unstable(feature = "array_chunks", issue = "74985")]

3
library/alloc/src/string.rs
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@ -49,6 +49,7 @@ use core::iter::{FromIterator, FusedIterator};
use core::ops::Bound::{Excluded, Included, Unbounded};
use core::ops::{self, Add, AddAssign, Index, IndexMut, Range, RangeBounds};
use core::ptr;
use core::slice;
use core::str::{lossy, pattern::Pattern};
use crate::borrow::{Cow, ToOwned};
@ -1506,7 +1507,7 @@ impl String {
// of the vector version. The data is just plain bytes.
// Because the range removal happens in Drop, if the Drain iterator is leaked,
// the removal will not happen.
let Range { start, end } = self.as_bytes().check_range(range);
let Range { start, end } = slice::check_range(self.len(), range);
assert!(self.is_char_boundary(start));
assert!(self.is_char_boundary(end));

2
library/alloc/src/vec.rs
View File

@ -1310,7 +1310,7 @@ impl<T> Vec<T> {
// the hole, and the vector length is restored to the new length.
//
let len = self.len();
let Range { start, end } = self.check_range(range);
let Range { start, end } = slice::check_range(len, range);
unsafe {
// set self.vec length's to start, to be safe in case Drain is leaked

2
library/alloc/tests/vec.rs
View File

@ -894,7 +894,7 @@ fn test_from_iter_partially_drained_in_place_specialization() {
#[test]
fn test_from_iter_specialization_with_iterator_adapters() {
fn assert_in_place_trait<T: InPlaceIterable>(_: &T) {};
let src: Vec<usize> = vec![0usize; if cfg!(miri) { 256 } else { 65535 }];
let src: Vec<usize> = vec![0usize; 256];
let srcptr = src.as_ptr();
let iter = src
.into_iter()

75
library/core/src/slice/index.rs
View File

@ -1,6 +1,6 @@
//! Indexing implementations for `[T]`.
use crate::ops;
use crate::ops::{self, Bound, Range, RangeBounds};
use crate::ptr;
#[stable(feature = "rust1", since = "1.0.0")]
@ -62,6 +62,79 @@ pub(super) fn slice_end_index_overflow_fail() -> ! {
panic!("attempted to index slice up to maximum usize");
}
/// Performs bounds-checking of the given range.
/// The returned [`Range`] is safe to pass to [`get_unchecked`] and [`get_unchecked_mut`]
/// for slices of the given length.
///
/// [`get_unchecked`]: ../../std/primitive.slice.html#method.get_unchecked
/// [`get_unchecked_mut`]: ../../std/primitive.slice.html#method.get_unchecked_mut
///
/// # Panics
///
/// Panics if the range is out of bounds.
///
/// # Examples
///
/// ```
/// #![feature(slice_check_range)]
/// use std::slice;
///
/// let v = [10, 40, 30];
/// assert_eq!(1..2, slice::check_range(v.len(), 1..2));
/// assert_eq!(0..2, slice::check_range(v.len(), ..2));
/// assert_eq!(1..3, slice::check_range(v.len(), 1..));
/// ```
///
/// Panics when [`Index::index`] would panic:
///
/// ```should_panic
/// #![feature(slice_check_range)]
///
/// std::slice::check_range(3, 2..1);
/// ```
///
/// ```should_panic
/// #![feature(slice_check_range)]
///
/// std::slice::check_range(3, 1..4);
/// ```
///
/// ```should_panic
/// #![feature(slice_check_range)]
///
/// std::slice::check_range(3, 1..=usize::MAX);
/// ```
///
/// [`Index::index`]: crate::ops::Index::index
#[track_caller]
#[unstable(feature = "slice_check_range", issue = "76393")]
pub fn check_range<R: RangeBounds<usize>>(len: usize, range: R) -> Range<usize> {
let start = match range.start_bound() {
Bound::Included(&start) => start,
Bound::Excluded(start) => {
start.checked_add(1).unwrap_or_else(|| slice_start_index_overflow_fail())
}
Bound::Unbounded => 0,
};
let end = match range.end_bound() {
Bound::Included(end) => {
end.checked_add(1).unwrap_or_else(|| slice_end_index_overflow_fail())
}
Bound::Excluded(&end) => end,
Bound::Unbounded => len,
};
if start > end {
slice_index_order_fail(start, end);
}
if end > len {
slice_end_index_len_fail(end, len);
}
Range { start, end }
}
mod private_slice_index {
use super::ops;
#[stable(feature = "slice_get_slice", since = "1.28.0")]

81
library/core/src/slice/mod.rs
View File

@ -12,7 +12,7 @@ use crate::cmp::Ordering::{self, Equal, Greater, Less};
use crate::intrinsics::assume;
use crate::marker::{self, Copy};
use crate::mem;
use crate::ops::{Bound, FnMut, Range, RangeBounds};
use crate::ops::{FnMut, Range, RangeBounds};
use crate::option::Option;
use crate::option::Option::{None, Some};
use crate::ptr::{self, NonNull};
@ -72,8 +72,8 @@ pub use sort::heapsort;
#[stable(feature = "slice_get_slice", since = "1.28.0")]
pub use index::SliceIndex;
use index::{slice_end_index_len_fail, slice_index_order_fail};
use index::{slice_end_index_overflow_fail, slice_start_index_overflow_fail};
#[unstable(feature = "slice_check_range", issue = "76393")]
pub use index::check_range;
#[lang = "slice"]
#[cfg(not(test))]
@ -378,79 +378,6 @@ impl<T> [T] {
unsafe { &mut *index.get_unchecked_mut(self) }
}
/// Converts a range over this slice to [`Range`].
///
/// The returned range is safe to pass to [`get_unchecked`] and [`get_unchecked_mut`].
///
/// [`get_unchecked`]: #method.get_unchecked
/// [`get_unchecked_mut`]: #method.get_unchecked_mut
///
/// # Panics
///
/// Panics if the range is out of bounds.
///
/// # Examples
///
/// ```
/// #![feature(slice_check_range)]
///
/// let v = [10, 40, 30];
/// assert_eq!(1..2, v.check_range(1..2));
/// assert_eq!(0..2, v.check_range(..2));
/// assert_eq!(1..3, v.check_range(1..));
/// ```
///
/// Panics when [`Index::index`] would panic:
///
/// ```should_panic
/// #![feature(slice_check_range)]
///
/// [10, 40, 30].check_range(2..1);
/// ```
///
/// ```should_panic
/// #![feature(slice_check_range)]
///
/// [10, 40, 30].check_range(1..4);
/// ```
///
/// ```should_panic
/// #![feature(slice_check_range)]
///
/// [10, 40, 30].check_range(1..=usize::MAX);
/// ```
///
/// [`Index::index`]: crate::ops::Index::index
#[track_caller]
#[unstable(feature = "slice_check_range", issue = "76393")]
pub fn check_range<R: RangeBounds<usize>>(&self, range: R) -> Range<usize> {
let start = match range.start_bound() {
Bound::Included(&start) => start,
Bound::Excluded(start) => {
start.checked_add(1).unwrap_or_else(|| slice_start_index_overflow_fail())
}
Bound::Unbounded => 0,
};
let len = self.len();
let end = match range.end_bound() {
Bound::Included(end) => {
end.checked_add(1).unwrap_or_else(|| slice_end_index_overflow_fail())
}
Bound::Excluded(&end) => end,
Bound::Unbounded => len,
};
if start > end {
slice_index_order_fail(start, end);
}
if end > len {
slice_end_index_len_fail(end, len);
}
Range { start, end }
}
/// Returns a raw pointer to the slice's buffer.
///
/// The caller must ensure that the slice outlives the pointer this
@ -2794,7 +2721,7 @@ impl<T> [T] {
where
T: Copy,
{
let Range { start: src_start, end: src_end } = self.check_range(src);
let Range { start: src_start, end: src_end } = check_range(self.len(), src);
let count = src_end - src_start;
assert!(dest <= self.len() - count, "dest is out of bounds");
// SAFETY: the conditions for `ptr::copy` have all been checked above,