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fix AsByteSliceMut using raw pointers with bad provenance #780

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Merged
merged 2 commits into from
Apr 20, 2019
Merged

fix AsByteSliceMut using raw pointers with bad provenance #780

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90501dc
fix AsByteSliceMut using raw pointers with bad provenance
RalfJung Apr 19, 2019
d9c611f
fix unaligned and illegal-provenance reads in next_u64
RalfJung Apr 19, 2019
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5 changes: 3 additions & 2 deletions rand_core/src/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@
//! [`fill_bytes`]: RngCore::fill_bytes

use core::convert::AsRef;
use core::fmt;
use core::{fmt, ptr};
use {RngCore, CryptoRng, SeedableRng, Error};
use impls::{fill_via_u32_chunks, fill_via_u64_chunks};

Expand Down Expand Up @@ -183,7 +183,8 @@ where <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
let read_u64 = |results: &[u32], index| {
if cfg!(any(target_arch = "x86", target_arch = "x86_64")) {
// requires little-endian CPU supporting unaligned reads:
unsafe { *(&results[index] as *const u32 as *const u64) }
let ptr: *const u64 = results[index..index+1].as_ptr() as *const u64;
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This range still only covers 1 element, not 2 elements, as it uses .. instead of ..=.

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Yeah, I fixed that in #784

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Didn't notice that commit :)

unsafe { ptr::read_unaligned(ptr) }
} else {
let x = u64::from(results[index]);
let y = u64::from(results[index + 1]);
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3 changes: 1 addition & 2 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -387,8 +387,7 @@ macro_rules! impl_as_byte_slice {
}
} else {
unsafe {
slice::from_raw_parts_mut(&mut self[0]
as *mut $t
slice::from_raw_parts_mut(self.as_mut_ptr()
as *mut u8,
self.len() * mem::size_of::<$t>()
)
Expand Down