From c6ad69d1d467580455aacc2399e155610f76def6 Mon Sep 17 00:00:00 2001
From: Josh Gao <jmgao@google.com>
Date: Mon, 25 Mar 2019 14:55:39 -0700
Subject: [PATCH] liblog: don't return 0xFFFFFFFF as an invalid log id.
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There are a bunch of branches that check "id >= LOG_ID_MAX", but because
C++ hates you, this does a promotion to signed int despite the
fact that both sides of the comparison are the same enum with an
underlying type of unsigned int. (C++17 §7.6.3)

Return LOG_ID_MAX instead of a value that gets promoted to signed -1, to
avoid this.

Bug: http://b/129272512
Test: /data/nativetest64/logcat-unit-tests/logcat-unit-tests
Change-Id: I4b3ee662d76d5cc80d9a9625d17f7e5b5980de41
---
 liblog/logger_name.cpp       |  6 ++++--
 logcat/tests/logcat_test.cpp | 11 +++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/liblog/logger_name.cpp b/liblog/logger_name.cpp
index 3aa684132..ece05505b 100644
--- a/liblog/logger_name.cpp
+++ b/liblog/logger_name.cpp
@@ -50,8 +50,9 @@ log_id_t android_name_to_log_id(const char* logName) {
   unsigned int ret;
 
   if (!logName) {
-    return static_cast<log_id_t>(0xFFFFFFFF);
+    return static_cast<log_id_t>(LOG_ID_MAX);
   }
+
   b = strrchr(logName, '/');
   if (!b) {
     b = logName;
@@ -65,5 +66,6 @@ log_id_t android_name_to_log_id(const char* logName) {
       return static_cast<log_id_t>(ret);
     }
   }
-  return static_cast<log_id_t>(0xFFFFFFFF); /* should never happen */
+
+  return static_cast<log_id_t>(LOG_ID_MAX);
 }
diff --git a/logcat/tests/logcat_test.cpp b/logcat/tests/logcat_test.cpp
index d5c40bec0..b32b43737 100644
--- a/logcat/tests/logcat_test.cpp
+++ b/logcat/tests/logcat_test.cpp
@@ -33,6 +33,7 @@
 #include <android-base/file.h>
 #include <android-base/macros.h>
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 #include <gtest/gtest.h>
 #include <log/event_tag_map.h>
 #include <log/log.h>
@@ -1747,3 +1748,13 @@ TEST(logcat, help) {
     EXPECT_EQ(logcatHelpTextSize * 2, logcatLastHelpTextSize);
 #endif
 }
+
+TEST(logcat, invalid_buffer) {
+  FILE* fp = popen("logcat -b foo 2>&1", "r");
+  ASSERT_NE(nullptr, fp);
+  std::string output;
+  ASSERT_TRUE(android::base::ReadFdToString(fileno(fp), &output));
+  pclose(fp);
+
+  ASSERT_TRUE(android::base::StartsWith(output, "unknown buffer foo\n"));
+}