HistoryEdit

RUSTSEC-2020-0061

futures_task::noop_waker_ref can segfault due to dereferencing a NULL pointer

Issued
Package
futures-task (crates.io)
Type
Vulnerability
Categories
Keywords
#NULL-pointer-dereference #memory-management
Aliases
Details
https://github.com/rust-lang/futures-rs/issues/2091
CVSS Score
5.5 MEDIUM
CVSS Details
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Patched
  • >=0.3.5
Keywords
#NULL-pointer-dereference #memory-management
Affected Functions
Version
futures_task::noop_waker_ref
  • >=0.3.0

Description

Affected versions of the crate used a UnsafeCell in thread-local storage to return a noop waker reference, assuming that the reference would never be returned from another thread.

This resulted in a segmentation fault crash if Waker::wake_by_ref() was called on a waker returned from another thread due to it attempting to dereference a pointer that wasn't accessible from the main thread.

Reproduction Example (from issue):

use futures_task::noop_waker_ref;
fn main() {
    let waker = std::thread::spawn(|| noop_waker_ref()).join().unwrap();
    waker.wake_by_ref();
}

The flaw was corrected by using a OnceCell::Lazy<> wrapper around the noop waker instead of thread-local storage.