Hello, we (Rust group @sslab-gatech) found a memory-safety/soundness issue in this crate while scanning Rust code on crates.io for potential vulnerabilities.
foo() method creates an uninitialized buffer and passes it to user-provided Read implementation. This is unsound, because it allows safe Rust code to exhibit an undefined behavior (read from uninitialized memory).
In case a user-provided Read reads from the given buffer, uninitialized buffer can make safe Rust code to cause memory safety errors by miscompilation. Uninitialized values are lowered to LLVM as llvm::UndefValue which may take different random values for each read. Propagation of UndefValue can quickly cause safe Rust code to exhibit undefined behavior.
This part from the Read trait documentation explains the issue:
It is your responsibility to make sure that
bufis initialized before callingread. Calling read with an uninitializedbuf(of the kind one obtains viaMaybeUninit<T>) is not safe, and can lead to undefined behavior.
The Naive & safe way to fix the issue is to always zero-initialize a buffer before lending it to a user-provided Read implementation. Note that this approach will add runtime performance overhead of zero-initializing the buffer.
As of Feb 2021, there is not yet an ideal fix that works with no performance overhead. Below are links to relevant discussions & suggestions for the fix.