Merge #1824

1824: fix bugs on android armv7, because `pw.pw_passwd.is_null()` r=rtzoeller a=ClarkGuan

crash on my Android phone because `pw.pw_passwd == NULL`

Co-authored-by: wdsgyj <gongbo.guan@momenta.ai>

Author: bors[bot]

CHANGELOG.md

@@ -27,6 +27,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - Fix `User::from_name` and `Group::from_name` panicking
   when given a name containing a nul.
   ([#1815](https://github.com/nix-rust/nix/pull/1815))
+- Fix `User::from_uid` and `User::from_name` crash on Android platform.
+  ([#1824](https://github.com/nix-rust/nix/pull/1824))
 
 ### Removed
 

src/unistd.rs

@@ -2984,12 +2984,12 @@ impl From<&libc::passwd> for User {
     fn from(pw: &libc::passwd) -> User {
         unsafe {
             User {
-                name: CStr::from_ptr(pw.pw_name).to_string_lossy().into_owned(),
-                passwd: CString::new(CStr::from_ptr(pw.pw_passwd).to_bytes()).unwrap(),
+                name: if pw.pw_name.is_null() { Default::default() } else { CStr::from_ptr(pw.pw_name).to_string_lossy().into_owned() },
+                passwd: if pw.pw_passwd.is_null() { Default::default() } else { CString::new(CStr::from_ptr(pw.pw_passwd).to_bytes()).unwrap() },
                 #[cfg(not(all(target_os = "android", target_pointer_width = "32")))]
-                gecos: CString::new(CStr::from_ptr(pw.pw_gecos).to_bytes()).unwrap(),
-                dir: PathBuf::from(OsStr::from_bytes(CStr::from_ptr(pw.pw_dir).to_bytes())),
-                shell: PathBuf::from(OsStr::from_bytes(CStr::from_ptr(pw.pw_shell).to_bytes())),
+                gecos: if pw.pw_gecos.is_null() { Default::default() } else { CString::new(CStr::from_ptr(pw.pw_gecos).to_bytes()).unwrap() },
+                dir: if pw.pw_dir.is_null() { Default::default() } else { PathBuf::from(OsStr::from_bytes(CStr::from_ptr(pw.pw_dir).to_bytes())) },
+                shell: if pw.pw_shell.is_null() { Default::default() } else { PathBuf::from(OsStr::from_bytes(CStr::from_ptr(pw.pw_shell).to_bytes())) },
                 uid: Uid::from_raw(pw.pw_uid),
                 gid: Gid::from_raw(pw.pw_gid),
                 #[cfg(not(any(target_os = "android",