ksud: fix mount view of manager when 'umount modules by default' is enabled

userspace/ksud/src/module.rs

@@ -11,6 +11,9 @@ use const_format::concatcp;
 use is_executable::is_executable;
 use java_properties::PropertiesIter;
 use log::{info, warn};
+#[cfg(any(target_os = "linux", target_os = "android"))]
+use rustix::{fd::AsFd, fs::CWD, mount::*};
+
 use std::{
     collections::HashMap,
     env::var as env_var,
@@ -706,17 +709,53 @@ pub fn shrink_ksu_images() -> Result<()> {
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub fn link_module_for_manager(pid: i32, pkg: &str, mid: &str) -> Result<()> {
-    // switch to manager's mnt ns
+    let from = PathBuf::from(defs::MODULE_DIR)
-    utils::switch_mnt_ns(pid)?;
-    let target = PathBuf::from("/data/data").join(pkg).join("webroot");
-
-    // umount previous mount
-    let _ = mount::umount_dir(&target);
-
-    let src = PathBuf::from(defs::MODULE_DIR)
         .join(mid)
         .join(defs::MODULE_WEB_DIR);
-    mount::bind_mount(src, &target)?;
+
+    let to = PathBuf::from("/data/data").join(pkg).join("webroot");
+
+    if let Result::Ok(tree) = open_tree(
+        rustix::fs::CWD,
+        &from,
+        OpenTreeFlags::OPEN_TREE_CLOEXEC
+            | OpenTreeFlags::OPEN_TREE_CLONE
+            | OpenTreeFlags::AT_RECURSIVE,
+    ) {
+        switch_mnt_ns(pid)?;
+
+        // umount previous mount
+        let _ = mount::umount_dir(&to);
+
+        if let Err(e) = move_mount(
+            tree.as_fd(),
+            "",
+            CWD,
+            &to,
+            MoveMountFlags::MOVE_MOUNT_F_EMPTY_PATH,
+        ) {
+            log::error!("move_mount failed: {}", e);
+        }
+    } else {
+        log::info!("fallback to bind mount");
+        // switch to manager's mnt ns
+        utils::switch_mnt_ns(pid)?;
+        if !Path::new(&from).exists() {
+            // maybe it is umounted, mount it back
+            log::info!("module web dir not exists, try to mount it back.");
+            mount::AutoMountExt4::try_new(defs::MODULE_IMG, defs::MODULE_DIR, false)
+                .with_context(|| "mount module image failed".to_string())?;
+        }
+
+        // umount previous mount
+        let _ = mount::umount_dir(&to);
+
+        if let Err(e) = rustix::mount::mount(&from, &to, "", MountFlags::BIND | MountFlags::REC, "")
+        {
+            log::error!("mount failed: {}", e);
+        }
+    }
+
     Ok(())
 }
 

userspace/ksud/src/mount.rs

@@ -3,7 +3,6 @@ use anyhow::{anyhow, bail, Ok, Result};
 #[cfg(any(target_os = "linux", target_os = "android"))]
 use anyhow::Context;
 #[cfg(any(target_os = "linux", target_os = "android"))]
-#[cfg(any(target_os = "linux", target_os = "android"))]
 use rustix::{fd::AsFd, fs::CWD, mount::*};
 
 use crate::defs::KSU_OVERLAY_SOURCE;