From ce566831eb188b0fdb27962e154b8da6103071bf Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Sat, 31 Jan 2026 11:27:25 -0800
Subject: [PATCH 1/3] fix: check ptr nullity before calling from_raw_parts

---
 src/buf.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/buf.rs b/src/buf.rs
index fd2bcbf96f..bfbc8dcc5c 100644
--- a/src/buf.rs
+++ b/src/buf.rs
@@ -44,12 +44,18 @@ impl Buf {
 impl Deref for Buf {
     type Target = [u8];
     fn deref(&self) -> &[u8] {
+        if self.raw.ptr.is_null() {
+            return &[];
+        }
         unsafe { slice::from_raw_parts(self.raw.ptr as *const u8, self.raw.size as usize) }
     }
 }
 
 impl DerefMut for Buf {
     fn deref_mut(&mut self) -> &mut [u8] {
+        if self.raw.ptr.is_null() {
+            return &mut [];
+        }
         unsafe { slice::from_raw_parts_mut(self.raw.ptr as *mut u8, self.raw.size as usize) }
     }
 }

From 73a5d5d7c49a7eb9d17c2ab6e40dafe3765ebf4d Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Sun, 1 Feb 2026 07:49:07 -0800
Subject: [PATCH 2/3] Add test for dereference of an empty Buf

---
 src/buf.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/buf.rs b/src/buf.rs
index bfbc8dcc5c..7b714dfe9c 100644
--- a/src/buf.rs
+++ b/src/buf.rs
@@ -75,3 +75,12 @@ impl Drop for Buf {
         unsafe { raw::git_buf_dispose(&mut self.raw) }
     }
 }
+
+#[test]
+fn empty_buf() {
+    let mut buf = Buf::new();
+    let x: &[u8] = &*buf;
+    assert_eq!(x.len(), 0);
+    let x: &mut [u8] = &mut *buf;
+    assert_eq!(x.len(), 0);
+}

From 0b274f76f70f717c3bda4be1f79ba8e1cb11afd4 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Mon, 2 Feb 2026 10:01:36 +0800
Subject: [PATCH 3/3] Bump to 0.20.4

---
 CHANGELOG.md | 8 ++++++++
 Cargo.lock   | 2 +-
 Cargo.toml   | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8770482b8f..3606f4027a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.20.4 - 2026-02-02
+[0.20.3...0.20.4](https://github.com/rust-lang/git2-rs/compare/git2-0.20.3...git2-0.20.4)
+
+### Fixed
+
+- Fix undefined behavior when dereferencing empty `Buf`.
+  [#1213](https://github.com/rust-lang/git2-rs/pull/1213)
+
 ## 0.20.3 - 2025-12-06
 [0.20.2...0.20.3](https://github.com/rust-lang/git2-rs/compare/git2-0.20.2...git2-0.20.3)
 
diff --git a/Cargo.lock b/Cargo.lock
index 0699b3fd3a..0aae751aef 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -357,7 +357,7 @@ dependencies = [
 
 [[package]]
 name = "git2"
-version = "0.20.3"
+version = "0.20.4"
 dependencies = [
  "bitflags 2.6.0",
  "clap",
diff --git a/Cargo.toml b/Cargo.toml
index 8e6e4cafbe..d9914c4336 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "git2"
-version = "0.20.3"
+version = "0.20.4"
 authors = ["Josh Triplett <josh@joshtriplett.org>", "Alex Crichton <alex@alexcrichton.com>"]
 license = "MIT OR Apache-2.0"
 readme = "README.md"