The first involved a panic-safety problem in Rust’s MapWindows::clone implementation. The function created a buffer before fully initializing its contents and then called a user-provided clone operation to populate it. If that operation triggered a panic, Rust’s unwinding mechanism could invoke the buffer’s destructor, which would attempt to access uninitialized memory. Microsoft said the reported fix prevents the partially initialized buffer from being destroyed before initialization is complete.
Another finding involved str::replace. The researchers found that the function could make an incorrect assumption about a custom implementation of the nightly Pattern trait. A custom implementation could supply a non-ASCII byte where the code expected an ASCII character, causing the replacement operation to produce invalid UTF-8 data. Subsequent string operations could then trigger undefined behavior, Microsoft said.
System-level bugs affect stable Rust
Microsoft said the first two categories of weaknesses were already being studied in 2021 through Rudra, a static analyzer developed by members of the research team. The standard library had also addressed panic-safety problems as far back as 2015, but similar weaknesses continue to appear in its implementations.
