From 6a00d3eb58d25f9b22aecfce9cb42f6b3ba9f84b Mon Sep 17 00:00:00 2001
From: Alan Somers <asomers@gmail.com>
Date: Fri, 22 Apr 2022 11:49:34 -0600
Subject: [PATCH] Fix UnixAddr::size on Linux and Android

SockaddrLike::size() is meant to return the amount of space that can be
used to store the sockaddr.  But on Linux-based OSes, UnixAddr contains
an extra field to store the address's length.  This field is not part of
the address, and should not contribute to the value of size().

This bug can't cause an out-of-bounds write, and every OS that we test
on can tolerate the greater-than-expected length, but it might confuse
applications that implement functions similar to getsockname in
userland.
---
 CHANGELOG.md           | 10 ++++++++++
 src/sys/socket/addr.rs | 44 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c5a2678a15..88f8df2a58 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,16 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
+## [Unreleased] - ReleaseDate
+### Added
+### Changed
+### Fixed
+
+- Fixed `UnixAddr::size` on Linux-based OSes.
+  (#[1702](https://github.com/nix-rust/nix/pull/1702))
+
+### Removed
+
 ## [0.24.0] - 2022-04-21
 ### Added
 
diff --git a/src/sys/socket/addr.rs b/src/sys/socket/addr.rs
index e2321cb7e8..18ff1c2c68 100644
--- a/src/sys/socket/addr.rs
+++ b/src/sys/socket/addr.rs
@@ -953,6 +953,10 @@ impl SockaddrLike for UnixAddr {
         ptr::copy(addr as *const u8, sup, su_len as usize);
         Some(Self::from_raw_parts(su, su_len as u8))
     }
+
+    fn size() -> libc::socklen_t where Self: Sized {
+        mem::size_of::<libc::sockaddr_un>() as libc::socklen_t
+    }
 }
 
 impl AsRef<libc::sockaddr_un> for UnixAddr {
@@ -2615,11 +2619,12 @@ mod tests {
     }
 
     mod link {
+        use super::*;
         #[cfg(any(target_os = "ios",
                   target_os = "macos",
                   target_os = "illumos"
                   ))]
-        use super::{*, super::super::socklen_t};
+        use super::super::super::socklen_t;
 
         /// Don't panic when trying to display an empty datalink address
         #[cfg(any(target_os = "dragonfly",
@@ -2701,6 +2706,25 @@ mod tests {
             assert_eq!(sock_addr.as_link_addr().unwrap().addr(),
                     Some([24u8, 101, 144, 221, 76, 176]));
         }
+
+        #[test]
+        fn size() {
+            #[cfg(any(target_os = "dragonfly",
+                      target_os = "freebsd",
+                      target_os = "ios",
+                      target_os = "macos",
+                      target_os = "netbsd",
+                      target_os = "illumos",
+                      target_os = "openbsd"))]
+            let l = mem::size_of::<libc::sockaddr_dl>();
+            #[cfg(any(
+                    target_os = "android",
+                    target_os = "fuchsia",
+                    target_os = "illumos",
+                    target_os = "linux"))]
+            let l = mem::size_of::<libc::sockaddr_ll>();
+            assert_eq!( LinkAddr::size() as usize, l);
+        }
     }
 
     mod sockaddr_in {
@@ -2713,6 +2737,12 @@ mod tests {
             let addr = SockaddrIn::from_str(s).unwrap();
             assert_eq!(s, format!("{}", addr));
         }
+
+        #[test]
+        fn size() {
+            assert_eq!(mem::size_of::<libc::sockaddr_in>(),
+                SockaddrIn::size() as usize);
+        }
     }
 
     mod sockaddr_in6 {
@@ -2725,10 +2755,15 @@ mod tests {
             let addr = SockaddrIn6::from_str(s).unwrap();
             assert_eq!(s, format!("{}", addr));
         }
+
+        #[test]
+        fn size() {
+            assert_eq!(mem::size_of::<libc::sockaddr_in6>(),
+                SockaddrIn6::size() as usize);
+        }
     }
 
     mod unixaddr {
-        #[cfg(any(target_os = "android", target_os = "linux"))]
         use super::*;
 
         #[cfg(any(target_os = "android", target_os = "linux"))]
@@ -2742,5 +2777,10 @@ mod tests {
             assert_eq!(sun_path1, sun_path2);
         }
 
+        #[test]
+        fn size() {
+            assert_eq!(mem::size_of::<libc::sockaddr_un>(),
+                UnixAddr::size() as usize);
+        }
     }
 }