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`Read` on uninitialized buffer may cause UB
Hello fellow Rustacean, we (Rust group @sslab-gatech) found a memory-safety/soundness issue in this crate while scanning Rust code on crates.io for potential vulnerabilities.
Issue Description
https://github.com/zhihu/rucene/blob/5b55f842c2bb03beb96898d520e880c180c91adf/src/core/store/io/data_input.rs#L214-L220
core::store::io::data_input::DataInput::read_string()
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).
This part from the Read
trait documentation explains the issue:
It is your responsibility to make sure that
buf
is initialized before callingread
. Calling read with an uninitializedbuf
(of the kind one obtains viaMaybeUninit<T>
) is not safe, and can lead to undefined behavior.
How to fix the issue?
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.