From 4bfe963ad48a4864e2a35c4998328561dbced544 Mon Sep 17 00:00:00 2001
From: Danny Baumann <dannybaumann@web.de>
Date: Mon, 23 Sep 2013 11:00:35 +0200
Subject: [PATCH] Make emulated storage mounting consistent to Zygote.

- Mount in private namespace
- Mount in forked child
- Mount /storage/emulated/legacy

All of this is optional and must be enabled by setting the environment
variable MOUNT_EMULATED_STORAGE.

Change-Id: Ied9c4485e58ab26ba8e6eafcbe05bb75fe6fdc52
---
 Android.mk                |  2 +-
 Superuser/jni/Android.mk  |  4 +--
 Superuser/jni/su/daemon.c | 66 +++++++++++++++++++++++++++++++++++++----------
 3 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/Android.mk b/Android.mk
index 8030a7b..7887812 100644
--- a/Android.mk
+++ b/Android.mk
@@ -19,7 +19,7 @@ include $(CLEAR_VARS)
 LOCAL_MODULE := su
 LOCAL_MODULE_TAGS := eng debug optional
 LOCAL_FORCE_STATIC_EXECUTABLE := true
-LOCAL_STATIC_LIBRARIES := libc
+LOCAL_STATIC_LIBRARIES := libc libcutils
 LOCAL_C_INCLUDES := external/sqlite/dist
 LOCAL_SRC_FILES := Superuser/jni/su/su.c Superuser/jni/su/daemon.c Superuser/jni/su/activity.c Superuser/jni/su/db.c Superuser/jni/su/utils.c ../../sqlite/dist/sqlite3.c
 LOCAL_CFLAGS := -DSQLITE_OMIT_LOAD_EXTENSION -DREQUESTOR=\"$(SUPERUSER_PACKAGE)\"
diff --git a/Superuser/jni/Android.mk b/Superuser/jni/Android.mk
index 41542b9..ffb2abf 100644
--- a/Superuser/jni/Android.mk
+++ b/Superuser/jni/Android.mk
@@ -3,8 +3,8 @@ LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 
 LOCAL_MODULE := su
-LOCAL_LDFLAGS := -static
-LOCAL_STATIC_LIBRARIES := sqlite3
+LOCAL_FORCE_STATIC_EXECUTABLE := true
+LOCAL_STATIC_LIBRARIES := sqlite3 libcutils libc
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/sqlite3
 LOCAL_SRC_FILES := su/su.c su/activity.c su/db.c su/utils.c su/daemon.c
 include $(BUILD_EXECUTABLE)
diff --git a/Superuser/jni/su/daemon.c b/Superuser/jni/su/daemon.c
index 3c2f233..0042d24 100644
--- a/Superuser/jni/su/daemon.c
+++ b/Superuser/jni/su/daemon.c
@@ -15,6 +15,8 @@
 ** limitations under the License.
 */
 
+#define _GNU_SOURCE /* for unshare() */
+
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
@@ -34,7 +36,9 @@
 #include <stdarg.h>
 #include <sys/types.h>
 #include <pthread.h>
+#include <sched.h>
 #include <termios.h>
+#include <cutils/multiuser.h>
 
 #include "su.h"
 #include "utils.h"
@@ -91,6 +95,41 @@ static void write_string(int fd, char* val) {
     }
 }
 
+static void mount_emulated_storage(int user_id) {
+    const char *emulated_source = getenv("EMULATED_STORAGE_SOURCE");
+    const char *emulated_target = getenv("EMULATED_STORAGE_TARGET");
+    const char* legacy = getenv("EXTERNAL_STORAGE");
+
+    if (!emulated_source || !emulated_target) {
+        // No emulated storage is present
+        return;
+    }
+
+    // Create a second private mount namespace for our process
+    if (unshare(CLONE_NEWNS) < 0) {
+        PLOGE("unshare");
+        return;
+    }
+
+    if (mount("rootfs", "/", NULL, MS_SLAVE | MS_REC, NULL) < 0) {
+        PLOGE("mount rootfs as slave");
+        return;
+    }
+
+    // /mnt/shell/emulated -> /storage/emulated
+    if (mount(emulated_source, emulated_target, NULL, MS_BIND, NULL) < 0) {
+        PLOGE("mount emulated storage");
+    }
+
+    char target_user[PATH_MAX];
+    snprintf(target_user, PATH_MAX, "%s/%d", emulated_target, user_id);
+
+    // /mnt/shell/emulated/<user> -> /storage/emulated/legacy
+    if (mount(target_user, legacy, NULL, MS_BIND | MS_REC, NULL) < 0) {
+        PLOGE("mount legacy path");
+    }
+}
+
 static int run_daemon_child(int infd, int outfd, int errfd, int argc, char** argv) {
     if (-1 == dup2(outfd, STDOUT_FILENO)) {
         PLOGE("dup2 child outfd");
@@ -171,6 +210,7 @@ static int daemon_accept(int fd) {
         daemon_from_pid = credentials.pid;
     }
 
+    int mount_storage = read_int(fd);
     int argc = read_int(fd);
     if (argc < 0 || argc > 512) {
         LOGE("unable to allocate args: %d", argc);
@@ -291,6 +331,10 @@ static int daemon_accept(int fd) {
             outfd = pts;
         }
 
+        if (mount_storage) {
+            mount_emulated_storage(multiuser_get_user_id(daemon_from_uid));
+        }
+
         return run_daemon_child(infd, outfd, errfd, argc, argv);
     }
 
@@ -349,19 +393,6 @@ int run_daemon() {
     unlink(sun.sun_path);
     unlink(REQUESTOR_DAEMON_PATH);
 
-    /*
-     * Mount emulated storage, if present. Normally that's done by zygote,
-     * but as we're started via init, we have to do it ourselves.
-     */
-    const char *emulated_source = getenv("EMULATED_STORAGE_SOURCE");
-    const char *emulated_target = getenv("EMULATED_STORAGE_TARGET");
-    if (emulated_source && *emulated_source && emulated_target && *emulated_target) {
-        if (mount(emulated_source, emulated_target, NULL,
-                MS_BIND | MS_NOEXEC | MS_NOSUID, NULL) < 0) {
-            PLOGE("mount emulated storage");
-        }
-    }
-
     int previous_umask = umask(027);
     mkdir(REQUESTOR_DAEMON_PATH, 0777);
 
@@ -431,14 +462,21 @@ int connect_daemon(int argc, char *argv[]) {
     }
 
     LOGD("connecting client %d", getpid());
+
+    int mount_storage = getenv("MOUNT_EMULATED_STORAGE") != NULL;
+
     write_int(socketfd, getpid());
     write_int(socketfd, isatty(STDIN_FILENO));
     write_int(socketfd, uid);
     write_int(socketfd, getppid());
-    write_int(socketfd, argc);
+    write_int(socketfd, mount_storage);
+    write_int(socketfd, mount_storage ? argc - 1 : argc);
 
     int i;
     for (i = 0; i < argc; i++) {
+        if (i == 1 && mount_storage) {
+            continue;
+        }
         write_string(socketfd, argv[i]);
     }
 
-- 
2.11.0