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smallvec: Buffer overflow in insert_many #552

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26 changes: 26 additions & 0 deletions crates/smallvec/RUSTSEC-0000-0000.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
```toml
[advisory]
id = "RUSTSEC-0000-0000"
package = "smallvec"
date = "2021-01-08"
url = "https://github.com/servo/rust-smallvec/issues/252"
categories = ["memory-corruption"]
keywords = ["buffer-overflow", "heap-overflow", "unsound"]

[versions]
patched = [">= 0.6.14, < 1.0.0", ">= 1.6.1"]
unaffected = ["< 0.6.3"]

[affected]
functions = { "smallvec::SmallVec::insert_many" = [">= 0.6.3, < 0.6.14", ">= 1.0.0, < 1.6.1"] }
```

# Buffer overflow in SmallVec::insert_many

A bug in the `SmallVec::insert_many` method caused it to allocate a buffer that was smaller than needed. It then wrote past the end of the buffer, causing a buffer overflow and memory corruption on the heap.

This bug was only triggered if the iterator passed to `insert_many` yielded more items than the lower bound returned from its `size_hint` method.

The flaw was corrected in smallvec 0.6.14 and 1.6.1, by ensuring that additional space is always reserved for each item inserted. The fix also simplified the implementation of `insert_many` to use less unsafe code, so it is easier to verify its correctness.

Thank you to Yechan Bae (@Qwaz) and the Rust group at Georgia Tech’s SSLab for finding and reporting this bug.