From a7c156a9e3ed96678ac256e9ac0bda0df2f78c9e Mon Sep 17 00:00:00 2001
From: LoveSy <shana@zju.edu.cn>
Date: Tue, 14 Dec 2021 19:40:23 +0800
Subject: [PATCH] Further fix `oplus.fstab` support

* Further fix `oplus.fstab` support

In some oneplus devices, `oplus.fstab` does exists but `init` never
loaded it and those entries in `oplus.fstab` are written directly to
`fstab.qcom`. Previous implementation will introduce duplicate entries
to `fstab.qcom` and brick the device. This commit filters those entries
from `oplus.fstab` that are already in `fstab.qcom` and further filters
duplicated entries in `oplus.fstab` (keep only the last entry).

Fix #5016

* Fix UB

Since we moved entry, we need to explicitly copy its member.
For c++23 we can use `auto{}`.
---
 native/jni/init/init.hpp     |  2 ++
 native/jni/init/twostage.cpp | 44 ++++++++++++++++++++++++------------
 2 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/native/jni/init/init.hpp b/native/jni/init/init.hpp
index 409ed1d9f..75bc4b474 100644
--- a/native/jni/init/init.hpp
+++ b/native/jni/init/init.hpp
@@ -26,6 +26,8 @@ struct fstab_entry {
     fstab_entry() = default;
     fstab_entry(const fstab_entry &) = delete;
     fstab_entry(fstab_entry &&) = default;
+    fstab_entry &operator=(const fstab_entry&) = delete;
+    fstab_entry &operator=(fstab_entry&&) = default;
     void to_file(FILE *fp);
 };
 
diff --git a/native/jni/init/twostage.cpp b/native/jni/init/twostage.cpp
index b929435a1..92b8c4719 100644
--- a/native/jni/init/twostage.cpp
+++ b/native/jni/init/twostage.cpp
@@ -8,6 +8,7 @@
 
 #include <sys/mount.h>
 #include <map>
+#include <set>
 
 #include <magisk.hpp>
 #include <utils.hpp>
@@ -132,30 +133,43 @@ exit_loop:
     // Append oppo's custom fstab
     if (access("oplus.fstab", F_OK) == 0) {
         LOGD("Found fstab file: %s\n", "oplus.fstab");
-        vector<fstab_entry> oplus_fstab;
+        set<string> main_mount_point;
         map<string, string> bind_map;
+        map<string, fstab_entry> entry_map;
 
-        read_fstab_file("oplus.fstab", oplus_fstab);
+        // used to avoid duplication
+        for (auto &entry: fstab) {
+            main_mount_point.emplace(entry.mnt_point);
+        }
 
-        for (auto &entry : oplus_fstab) {
-            if (entry.mnt_flags.find("bind") != string::npos) {
-                bind_map.emplace(entry.dev, entry.mnt_point);
-                entry.dev = "";
+        {
+            vector<fstab_entry> oplus_fstab;
+            read_fstab_file("oplus.fstab", oplus_fstab);
+
+            for (auto &entry : oplus_fstab) {
+                // skip duplicated entry between the main file and the oplus one
+                if (main_mount_point.count(entry.mnt_point)) continue;
+                if (entry.mnt_flags.find("bind") != string::npos) {
+                    bind_map.emplace(std::move(entry.dev), std::move(entry.mnt_point));
+                } else {
+                    // skip duplicated entry in the same file
+                    entry_map.insert_or_assign(decltype(entry.mnt_point){entry.mnt_point}, std::move(entry));
+                }
             }
         }
 
-        for (auto &entry : oplus_fstab) {
-            // Merge bind entries
-            if (entry.dev.empty())
-                continue;
-            auto got = bind_map.find(entry.mnt_point);
-            if (got != bind_map.end())
-                entry.mnt_point = got->second;
-
-            // Mount befor switch root, fix img path
+        for (auto &[_, entry] : entry_map) {
+            // Mount before switch root, fix img path
             if (str_starts(entry.dev, "loop@/system/"))
                 entry.dev.insert(5, "/system_root");
 
+            // change bind mount entries to dev mount since some users reported bind is not working
+            // in this case, we drop the original mount point and leave only the one from bind entry
+            // because some users reported keeping the original mount point causes bootloop
+            if (auto got = bind_map.find(entry.mnt_point); got != bind_map.end()) {
+                entry.mnt_point = got->second;
+            }
+
             fstab.push_back(move(entry));
         }