commit 0ab0615f8cf549919c3e06ed9f99239d03700fa2
author Nate Myren <ntmyren@google.com> Thu Oct 19 16:50:59 2023 -0700
committer Nate Myren <ntmyren@google.com> Wed Oct 25 17:41:33 2023 -0700
tree e1daa1c9c2213ae8c69d020faf4ce6e2c0beff27
parent b8c87b14b065e79c7ba7f39f5ab4c7fdc6354f04

Move __system_properties_reload to LIBC from LIBC_PLATFORM

The zygote cannot have visiblity to LIBC_PLATFORM methods. Therefore,
move __system_properties_reload to LIBC, and rename it
__system_properties_zygote_reload, and indicate in comments that it
should not be used by non-zygote apps

Bug: 291814949
Test: atest CtsBionicRootTestCases
Change-Id: Iee8fa0c76b740543c05a433393f2f4bef36d6d3d

libc/bionic/system_property_api.cpp

diff --git a/libc/bionic/system_property_api.cpp b/libc/bionic/system_property_api.cpp
index 847473a..8fdea59 100644
--- a/libc/bionic/system_property_api.cpp
+++ b/libc/bionic/system_property_api.cpp
@@ -29,6 +29,7 @@
 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
 #include <sys/_system_properties.h>
 
+#include <async_safe/CHECK.h>
 #include <system_properties/prop_area.h>
 #include <system_properties/system_properties.h>
 
@@ -131,6 +132,7 @@
 }
 
 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
-int __system_properties_reload() {
+int __system_properties_zygote_reload(void) {
+  CHECK(getpid() == gettid());
   return system_properties.Reload(false) ? 0 : -1;
 }

libc/include/sys/_system_properties.h

diff --git a/libc/include/sys/_system_properties.h b/libc/include/sys/_system_properties.h
index 098f355..30dea89 100644
--- a/libc/include/sys/_system_properties.h
+++ b/libc/include/sys/_system_properties.h
@@ -131,13 +131,15 @@
 
 /*
  * Reloads the system properties from disk.
+ * Not intended for use by any apps except the Zygote. Should only be called from the main thread.
  *
  * NOTE: Any pointers received from methods such as __system_property_find should be assumed to be
  * invalid after this method is called.
  *
- * Returns 0 on success, -1 otherwise
+ * Returns 0 on success, -1 if the system properties failed to re-initialize (same conditions as
+ * __system properties_init)
  */
-int __system_properties_reload();
+int __system_properties_zygote_reload(void); __INTRODUCED_IN(__ANDROID_API_V__)
 
 /* Deprecated: use __system_property_wait instead. */
 uint32_t __system_property_wait_any(uint32_t __old_serial);

libc/libc.map.txt

diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index d737946..156e9ee 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1600,6 +1600,7 @@
     tzalloc;
     tzfree;
     wcsrtombs_l;
+    __system_properties_zygote_reload; # apex
 } LIBC_U;
 
 LIBC_PRIVATE {
@@ -1806,7 +1807,6 @@
     __system_property_area_init;
     __system_property_set_filename;
     __system_property_update;
-    __system_properties_reload;
     android_fdsan_get_fd_table;
     android_fdtrack_compare_exchange_hook; # llndk
     android_fdtrack_get_enabled; # llndk

libc/system_properties/system_properties.cpp

diff --git a/libc/system_properties/system_properties.cpp b/libc/system_properties/system_properties.cpp
index e0b771c..9dd5e35 100644
--- a/libc/system_properties/system_properties.cpp
+++ b/libc/system_properties/system_properties.cpp
@@ -382,8 +382,8 @@
     } else if (is_override) {
       // We already wrote the ro.*, but appcompat_override.ro.* should override that. We don't
       // need to do the usual dirty bit setting, as this only happens during the init process,
-      // before any readers are started.
-      CHECK(getpid() == 1);
+      // before any readers are started. Check that only init or root can write appcompat props.
+      CHECK(getpid() == 1 || getuid() == 0);
       atomic_thread_fence(memory_order_release);
       strlcpy(other_pi->value, value, valuelen + 1);
     }