From f12af5e90727869d225f169e7f475695da64bf48 Mon Sep 17 00:00:00 2001
From: Martin Wallgren <martin.wallgren@sonymobile.com>
Date: Tue, 11 Aug 2015 15:10:31 +0200
Subject: RRO: Synchronize access to overlays.list

idmap --scan is executed as a part of the pre-loading in ZygoteInit.
The pre loading is executed in parallel for each supported architecture
(32/64 bit). This will cause a race condition in the creation of the
overlays.list file and the idmap files for the system overlays.

Apply flock on overlays.list to prevent the file from being thrown away
and recreated when it is in use by another Zygote.

Bug: 28032298

Change-Id: I51d39f121d207b11181340b68b164b60020f0c61
---
 libs/androidfw/AssetManager.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'libs/androidfw/AssetManager.cpp')

diff --git a/libs/androidfw/AssetManager.cpp b/libs/androidfw/AssetManager.cpp
index 8ea25d60cc89..07044d0e9d61 100644
--- a/libs/androidfw/AssetManager.cpp
+++ b/libs/androidfw/AssetManager.cpp
@@ -35,6 +35,9 @@
 #include <utils/threads.h>
 #include <utils/Timers.h>
 #include <utils/Trace.h>
+#ifndef _WIN32
+#include <sys/file.h>
+#endif
 
 #include <assert.h>
 #include <dirent.h>
@@ -767,6 +770,12 @@ void AssetManager::addSystemOverlays(const char* pathOverlaysList,
         return;
     }
 
+#ifndef _WIN32
+    if (TEMP_FAILURE_RETRY(flock(fileno(fin), LOCK_SH)) != 0) {
+        fclose(fin);
+        return;
+    }
+#endif
     char buf[1024];
     while (fgets(buf, sizeof(buf), fin)) {
         // format of each line:
@@ -797,6 +806,10 @@ void AssetManager::addSystemOverlays(const char* pathOverlaysList,
             const_cast<AssetManager*>(this)->mZipSet.addOverlay(targetPackagePath, oap);
         }
     }
+
+#ifndef _WIN32
+    TEMP_FAILURE_RETRY(flock(fileno(fin), LOCK_UN));
+#endif
     fclose(fin);
 }
 
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