Moved headers to includes, various changes...

+ Added better UID checks.
+ Added MS_SLAVE root mount in the new mount namespace.

module/jni/Android.mk

@@ -1,6 +1,7 @@
 LOCAL_PATH := $(call my-dir)
 
 include $(CLEAR_VARS)
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
 LOCAL_MODULE := zygisk
 LOCAL_SRC_FILES := mount_parser.cpp unmount.cpp main.cpp
 LOCAL_STATIC_LIBRARIES := libcxx

module/jni/include/android_filesystem_config.h

@@ -0,0 +1,219 @@
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * This file is consumed by build/tools/fs_config and is used
+ * for generating various files. Anything #define AID_<name>
+ * becomes the mapping for getpwnam/getpwuid, etc. The <name>
+ * field is lowercased.
+ * For example:
+ * #define AID_FOO_BAR 6666 becomes a friendly name of "foo_bar"
+ *
+ * The above holds true with the exception of:
+ *   mediacodec
+ *   mediaex
+ *   mediadrm
+ * Whose friendly names do not match the #define statements.
+ *
+ * This file must only be used for platform (Google managed, and submitted through AOSP), AIDs.  3rd
+ * party AIDs must be added via config.fs, which will place them in the corresponding partition's
+ * passwd and group files.  There are ranges in this file reserved for AIDs for each 3rd party
+ * partition, from which the system reads passwd and group files.
+ */
+
+#pragma once
+
+/* This is the main Users and Groups config for the platform.
+ * DO NOT EVER RENUMBER
+ */
+
+#define AID_ROOT 0 /* traditional unix root user */
+/* The following are for LTP and should only be used for testing */
+#define AID_DAEMON 1 /* traditional unix daemon owner */
+#define AID_BIN 2    /* traditional unix binaries owner */
+
+#define AID_SYSTEM 1000 /* system server */
+
+#define AID_RADIO 1001           /* telephony subsystem, RIL */
+#define AID_BLUETOOTH 1002       /* bluetooth subsystem */
+#define AID_GRAPHICS 1003        /* graphics devices */
+#define AID_INPUT 1004           /* input devices */
+#define AID_AUDIO 1005           /* audio devices */
+#define AID_CAMERA 1006          /* camera devices */
+#define AID_LOG 1007             /* log devices */
+#define AID_COMPASS 1008         /* compass device */
+#define AID_MOUNT 1009           /* mountd socket */
+#define AID_WIFI 1010            /* wifi subsystem */
+#define AID_ADB 1011             /* android debug bridge (adbd) */
+#define AID_INSTALL 1012         /* group for installing packages */
+#define AID_MEDIA 1013           /* mediaserver process */
+#define AID_DHCP 1014            /* dhcp client */
+#define AID_SDCARD_RW 1015       /* external storage write access */
+#define AID_VPN 1016             /* vpn system */
+#define AID_KEYSTORE 1017        /* keystore subsystem */
+#define AID_USB 1018             /* USB devices */
+#define AID_DRM 1019             /* DRM server */
+#define AID_MDNSR 1020           /* MulticastDNSResponder (service discovery) */
+#define AID_GPS 1021             /* GPS daemon */
+#define AID_UNUSED1 1022         /* deprecated, DO NOT USE */
+#define AID_MEDIA_RW 1023        /* internal media storage write access */
+#define AID_MTP 1024             /* MTP USB driver access */
+#define AID_UNUSED2 1025         /* deprecated, DO NOT USE */
+#define AID_DRMRPC 1026          /* group for drm rpc */
+#define AID_NFC 1027             /* nfc subsystem */
+#define AID_SDCARD_R 1028        /* external storage read access */
+#define AID_CLAT 1029            /* clat part of nat464 */
+#define AID_LOOP_RADIO 1030      /* loop radio devices */
+#define AID_MEDIA_DRM 1031       /* MediaDrm plugins */
+#define AID_PACKAGE_INFO 1032    /* access to installed package details */
+#define AID_SDCARD_PICS 1033     /* external storage photos access */
+#define AID_SDCARD_AV 1034       /* external storage audio/video access */
+#define AID_SDCARD_ALL 1035      /* access all users external storage */
+#define AID_LOGD 1036            /* log daemon */
+#define AID_SHARED_RELRO 1037    /* creator of shared GNU RELRO files */
+#define AID_DBUS 1038            /* dbus-daemon IPC broker process */
+#define AID_TLSDATE 1039         /* tlsdate unprivileged user */
+#define AID_MEDIA_EX 1040        /* mediaextractor process */
+#define AID_AUDIOSERVER 1041     /* audioserver process */
+#define AID_METRICS_COLL 1042    /* metrics_collector process */
+#define AID_METRICSD 1043        /* metricsd process */
+#define AID_WEBSERV 1044         /* webservd process */
+#define AID_DEBUGGERD 1045       /* debuggerd unprivileged user */
+#define AID_MEDIA_CODEC 1046     /* mediacodec process */
+#define AID_CAMERASERVER 1047    /* cameraserver process */
+#define AID_FIREWALL 1048        /* firewalld process */
+#define AID_TRUNKS 1049          /* trunksd process (TPM daemon) */
+#define AID_NVRAM 1050           /* Access-controlled NVRAM */
+#define AID_DNS 1051             /* DNS resolution daemon (system: netd) */
+#define AID_DNS_TETHER 1052      /* DNS resolution daemon (tether: dnsmasq) */
+#define AID_WEBVIEW_ZYGOTE 1053  /* WebView zygote process */
+#define AID_VEHICLE_NETWORK 1054 /* Vehicle network service */
+#define AID_MEDIA_AUDIO 1055     /* GID for audio files on internal media storage */
+#define AID_MEDIA_VIDEO 1056     /* GID for video files on internal media storage */
+#define AID_MEDIA_IMAGE 1057     /* GID for image files on internal media storage */
+#define AID_TOMBSTONED 1058      /* tombstoned user */
+#define AID_MEDIA_OBB 1059       /* GID for OBB files on internal media storage */
+#define AID_ESE 1060             /* embedded secure element (eSE) subsystem */
+#define AID_OTA_UPDATE 1061      /* resource tracking UID for OTA updates */
+#define AID_AUTOMOTIVE_EVS 1062  /* Automotive rear and surround view system */
+#define AID_LOWPAN 1063          /* LoWPAN subsystem */
+#define AID_HSM 1064             /* hardware security module subsystem */
+#define AID_RESERVED_DISK 1065   /* GID that has access to reserved disk space */
+#define AID_STATSD 1066          /* statsd daemon */
+#define AID_INCIDENTD 1067       /* incidentd daemon */
+#define AID_SECURE_ELEMENT 1068  /* secure element subsystem */
+#define AID_LMKD 1069            /* low memory killer daemon */
+#define AID_LLKD 1070            /* live lock daemon */
+#define AID_IORAPD 1071          /* input/output readahead and pin daemon */
+#define AID_GPU_SERVICE 1072     /* GPU service daemon */
+#define AID_NETWORK_STACK 1073   /* network stack service */
+#define AID_GSID 1074            /* GSI service daemon */
+#define AID_FSVERITY_CERT 1075   /* fs-verity key ownership in keystore */
+#define AID_CREDSTORE 1076       /* identity credential manager service */
+#define AID_EXTERNAL_STORAGE 1077 /* Full external storage access including USB OTG volumes */
+#define AID_EXT_DATA_RW 1078      /* GID for app-private data directories on external storage */
+#define AID_EXT_OBB_RW 1079       /* GID for OBB directories on external storage */
+#define AID_CONTEXT_HUB 1080      /* GID for access to the Context Hub */
+/* Changes to this file must be made in AOSP, *not* in internal branches. */
+
+#define AID_SHELL 2000 /* adb and debug shell user */
+#define AID_CACHE 2001 /* cache access */
+#define AID_DIAG 2002  /* access to diagnostic resources */
+
+/* The range 2900-2999 is reserved for the vendor partition */
+/* Note that the two 'OEM' ranges pre-dated the vendor partition, so they take the legacy 'OEM'
+ * name. Additionally, they pre-dated passwd/group files, so there are users and groups named oem_#
+ * created automatically for all values in these ranges.  If there is a user/group in a passwd/group
+ * file corresponding to this range, both the oem_# and user/group names will resolve to the same
+ * value. */
+#define AID_OEM_RESERVED_START 2900
+#define AID_OEM_RESERVED_END 2999
+
+/* The 3000 series are intended for use as supplemental group id's only.
+ * They indicate special Android capabilities that the kernel is aware of. */
+#define AID_NET_BT_ADMIN 3001 /* bluetooth: create any socket */
+#define AID_NET_BT 3002       /* bluetooth: create sco, rfcomm or l2cap sockets */
+#define AID_INET 3003         /* can create AF_INET and AF_INET6 sockets */
+#define AID_NET_RAW 3004      /* can create raw INET sockets */
+#define AID_NET_ADMIN 3005    /* can configure interfaces and routing tables. */
+#define AID_NET_BW_STATS 3006 /* read bandwidth statistics */
+#define AID_NET_BW_ACCT 3007  /* change bandwidth statistics accounting */
+#define AID_READPROC 3009     /* Allow /proc read access */
+#define AID_WAKELOCK 3010     /* Allow system wakelock read/write access */
+#define AID_UHID 3011         /* Allow read/write to /dev/uhid node */
+
+/* The range 5000-5999 is also reserved for vendor partition. */
+#define AID_OEM_RESERVED_2_START 5000
+#define AID_OEM_RESERVED_2_END 5999
+
+/* The range 6000-6499 is reserved for the system partition. */
+#define AID_SYSTEM_RESERVED_START 6000
+#define AID_SYSTEM_RESERVED_END 6499
+
+/* The range 6500-6999 is reserved for the odm partition. */
+#define AID_ODM_RESERVED_START 6500
+#define AID_ODM_RESERVED_END 6999
+
+/* The range 7000-7499 is reserved for the product partition. */
+#define AID_PRODUCT_RESERVED_START 7000
+#define AID_PRODUCT_RESERVED_END 7499
+
+/* The range 7500-7999 is reserved for the system_ext partition. */
+#define AID_SYSTEM_EXT_RESERVED_START 7500
+#define AID_SYSTEM_EXT_RESERVED_END 7999
+
+#define AID_EVERYBODY 9997 /* shared between all apps in the same profile */
+#define AID_MISC 9998      /* access to misc storage */
+#define AID_NOBODY 9999
+
+#define AID_APP 10000       /* TODO: switch users over to AID_APP_START */
+#define AID_APP_START 10000 /* first app user */
+#define AID_APP_END 19999   /* last app user */
+
+#define AID_CACHE_GID_START 20000 /* start of gids for apps to mark cached data */
+#define AID_CACHE_GID_END 29999   /* end of gids for apps to mark cached data */
+
+#define AID_EXT_GID_START 30000 /* start of gids for apps to mark external data */
+#define AID_EXT_GID_END 39999   /* end of gids for apps to mark external data */
+
+#define AID_EXT_CACHE_GID_START 40000 /* start of gids for apps to mark external cached data */
+#define AID_EXT_CACHE_GID_END 49999   /* end of gids for apps to mark external cached data */
+
+#define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
+#define AID_SHARED_GID_END 59999   /* end of gids for apps in each user to share */
+
+/*
+ * This is a magic number in the kernel and not something that was picked
+ * arbitrarily. This value is returned whenever a uid that has no mapping in the
+ * user namespace is returned to userspace:
+ * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/highuid.h?h=v4.4#n40
+ */
+#define AID_OVERFLOWUID 65534 /* unmapped user in the user namespace */
+
+/* use the ranges below to determine whether a process is isolated */
+#define AID_ISOLATED_START 90000 /* start of uids for fully isolated sandboxed processes */
+#define AID_ISOLATED_END 99999   /* end of uids for fully isolated sandboxed processes */
+
+#define AID_USER 100000        /* TODO: switch users over to AID_USER_OFFSET */
+#define AID_USER_OFFSET 100000 /* offset for uid ranges for each user */
+
+/*
+ * android_ids has moved to pwd/grp functionality.
+ * If you need to add one, the structure is now
+ * auto-generated based on the AID_ constraints
+ * documented at the top of this header file.
+ * Also see build/tools/fs_config for more details.
+ */

module/jni/main.cpp

@@ -1,15 +1,28 @@
 #include <unistd.h>
 #include <sched.h>
 
+#include <sys/mount.h>
+
 #include "zygisk.hpp"
 #include "logging.hpp"
+#include "android_filesystem_config.h"
 
 using zygisk::Api;
 using zygisk::AppSpecializeArgs;
 using zygisk::ServerSpecializeArgs;
 
 void do_unmount();
 
+static int shouldSkipUid(int uid)
+{
+    int appid = uid % AID_USER_OFFSET;
+    if (appid >= AID_APP_START && appid <= AID_APP_END)
+        return false;
+    if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END)
+        return false;
+    return true;
+}
+
 class ZygiskModule : public zygisk::ModuleBase
 {
 public:
@@ -26,25 +39,35 @@ class ZygiskModule : public zygisk::ModuleBase
         uint32_t flags = api->getFlags();
         bool isRoot = (flags & zygisk::StateFlag::PROCESS_GRANTED_ROOT) != 0;
         bool isOnDenylist = (flags & zygisk::StateFlag::PROCESS_ON_DENYLIST) != 0;
-        if (!isRoot && isOnDenylist && args->uid > 1000)
+        if (isRoot || !isOnDenylist || shouldSkipUid(args->uid))
         {
-            LOGD("Unmounting in preAppSpecialize for pid=%d uid=%d", getpid(), args->uid);
-
-            /*
-             * preAppSpecialize is before ensureInAppMountNamespace.
-             * postAppSpecialize is after seccomp setup.
-             * So we unshare here to create a pseudo app mount namespace
-             */
-            if (unshare(CLONE_NEWNS) == 0)
-            {
-                LOGD("unshare(CLONE_NEWNS) returned 0");
-                do_unmount();
-            }
-            else
-            {
-                LOGE("unshare(CLONE_NEWNS) returned -1: %d (%s)", errno, strerror(errno));
-            }
+            return;
         }
+
+        LOGD("Unmounting in preAppSpecialize for pid=%d uid=%d", getpid(), args->uid);
+
+        /*
+         * preAppSpecialize is before ensureInAppMountNamespace.
+         * postAppSpecialize is after seccomp setup.
+         * So we unshare here to create a pseudo app mount namespace
+         */
+        if (unshare(CLONE_NEWNS) == -1)
+        {
+            LOGE("unshare(CLONE_NEWNS) returned -1: %d (%s)", errno, strerror(errno));
+            // Don't unmount anything in global namespace
+            return;
+        }
+
+        /*
+         * Mount the pseudo app mount namespace's root as MS_SLAVE, so every mount/umount from
+         * Zygote shared pre-specialization mountspace is propagated to this one.
+         */
+        if (mount("rootfs", "/", NULL, (MS_SLAVE | MS_REC), NULL) == -1)
+        {
+            LOGE("mount(\"rootfs\", \"/\", NULL, (MS_SLAVE | MS_REC), NULL) returned -1");
+        }
+
+        do_unmount();
     }
 
 private: