From aba9024849ad0b1500864417bb7136a901381513 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maciej=20=C5=BBenczykowski?= <maze@google.com>
Date: Thu, 28 Jul 2022 09:15:48 +0000
Subject: [PATCH] detect inability to write to index != 0 of bpf map array
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(this is a test for a kernel bug)

Bug: 240347583
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I0cad47113a83dbd837cccc5229ef52b605cda203
---
 bpfloader/BpfLoader.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/bpfloader/BpfLoader.cpp b/bpfloader/BpfLoader.cpp
index b8dd504..ea49a38 100644
--- a/bpfloader/BpfLoader.cpp
+++ b/bpfloader/BpfLoader.cpp
@@ -274,6 +274,15 @@ int main(int argc, char** argv) {
         }
     }
 
+    int key = 1;
+    int value = 123;
+    android::base::unique_fd map(
+            android::bpf::createMap(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value), 2, 0));
+    if (android::bpf::writeToMapEntry(map, &key, &value, BPF_ANY)) {
+        ALOGE("Critical kernel bug - failure to write into index 1 of 2 element bpf map array.");
+        return 1;
+    }
+
     if (android::base::SetProperty("bpf.progs_loaded", "1") == false) {
         ALOGE("Failed to set bpf.progs_loaded property");
         return 1;