From d1b5d4ceb1645d0843729479a04be6c119a04369 Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Fri, 12 Aug 2022 12:22:43 +0200 Subject: [PATCH] Don't have important data in unused capacity when calling reserve (#563) --- src/bytes_mut.rs | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/bytes_mut.rs b/src/bytes_mut.rs index 2282bdc..a292ca7 100644 --- a/src/bytes_mut.rs +++ b/src/bytes_mut.rs @@ -705,6 +705,15 @@ impl BytesMut { new_cap = cmp::max(double, new_cap); // No space - allocate more + // + // The length field of `Shared::vec` is not used by the `BytesMut`; + // instead we use the `len` field in the `BytesMut` itself. However, + // when calling `reserve`, it doesn't guarantee that data stored in + // the unused capacity of the vector is copied over to the new + // allocation, so we need to ensure that we don't have any data we + // care about in the unused capacity before calling `reserve`. + debug_assert!(off + len <= v.capacity()); + v.set_len(off + len); v.reserve(new_cap - v.len()); // Update the info