From 89125658852f6895ebdcd684ff8c38b9fee80f31 Mon Sep 17 00:00:00 2001
From: Jeff Genovy <29107334+jefgen@users.noreply.github.com>
Date: Mon, 1 Feb 2021 12:14:24 -0800
Subject: [PATCH] Cherry-pick: ICU-21449 Infinite loop can occur with locale
 IDs that contain RES_PATH_SEPARATOR (#66)

This change cherry-picks the upstream fix for the issue of an infinite loop when calling various APIs with locale IDs that contain `RES_PATH_SEPARATOR`.

Upstream ticket:
https://unicode-org.atlassian.net/browse/ICU-21449

Upstream PR:
https://github.com/unicode-org/icu/pull/1549

Detailed Description (from the upstream PR):
When calling APIs like `uloc_getDisplayLanguage`, if the input locale ID has `/` (the `RES_PATH_SEPARATOR` value) then the resource look-up code ends up in an infinite loop.

For example, the following code will never return:

```c++
UErrorCode status = U_ZERO_ERROR;
const char* localeNameTemp = "/"; // RES_PATH_SEPARATOR
uloc_getDisplayLanguage(localeNameTemp, localeNameTemp, NULL, 0, &status);
```

The `do {...} while` loop in `ures_getByKeyWithFallback` calls `res_findResource`, but it never checks to see if the returned resource is `RES_BOGUS`, meaning that for some paths it will never terminate. (Thanks to am11 for doing the initial investigation into this issue.)

This PR also includes a test case for the issue. Note that there is nothing really "tested" by the test case, as the test is to simply ensure that calling the API doesn't cause a hang due to the infinite loop.
---
 icu/icu4c/source/common/uresbund.cpp     |  2 ++
 icu/icu4c/source/test/cintltst/cloctst.c | 16 ++++++++++++++--
 icu/icu4c/source/test/cintltst/cloctst.h |  2 +-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/icu/icu4c/source/common/uresbund.cpp b/icu/icu4c/source/common/uresbund.cpp
index 2ece87897d7..f17ba1be895 100644
--- a/icu/icu4c/source/common/uresbund.cpp
+++ b/icu/icu4c/source/common/uresbund.cpp
@@ -1908,6 +1908,8 @@ ures_getByKeyWithFallback(const UResourceBundle *resB,
                             } else {
                               break;
                             }
+                        } else if (res == RES_BOGUS) {
+                            break;
                         }
                     } while(*myPath); /* Continue until the whole path is consumed */
                 }
diff --git a/icu/icu4c/source/test/cintltst/cloctst.c b/icu/icu4c/source/test/cintltst/cloctst.c
index aeb2c2a64d0..cd930bae3ae 100644
--- a/icu/icu4c/source/test/cintltst/cloctst.c
+++ b/icu/icu4c/source/test/cintltst/cloctst.c
@@ -280,6 +280,7 @@ void addLocaleTest(TestNode** root)
     TESTCASE(TestBug20370);
     TESTCASE(TestBug20321UnicodeLocaleKey);
     TESTCASE(TestUsingDefaultWarning);
+    TESTCASE(TestBug21449InfiniteLoop);
 }
 
 
@@ -6980,11 +6981,12 @@ static void TestUsingDefaultWarning() {
         log_err("ERROR: in uloc_getDisplayKeywordValue %s %s return len:%d %s with status %d %s\n",
                 keyword_value, keyword, length, errorOutputBuff, status, myErrorName(status));
       }
-}      
+}
+
 // Test case for ICU-20575
 // This test checks if the environment variable LANG is set, 
 // and if so ensures that both C and C.UTF-8 cause ICU's default locale to be en_US_POSIX.
-static void TestCDefaultLocale(){
+static void TestCDefaultLocale() {
     const char *defaultLocale = uloc_getDefault();
     char *env_var = getenv("LANG");
     if (env_var == NULL) {
@@ -6995,3 +6997,13 @@ static void TestCDefaultLocale(){
       log_err("The default locale for LANG=%s should be en_US_POSIX, not %s\n", env_var, defaultLocale);
     }
 }
+
+// Test case for ICU-21449
+static void TestBug21449InfiniteLoop() {
+    UErrorCode status = U_ZERO_ERROR;
+    const char* invalidLocaleId = RES_PATH_SEPARATOR_S;
+
+    // The issue causes an infinite loop to occur when looking up a non-existent resource for the invalid locale ID,
+    // so the test is considered passed if the call to the API below returns anything at all.
+    uloc_getDisplayLanguage(invalidLocaleId, invalidLocaleId, NULL, 0, &status);
+}
diff --git a/icu/icu4c/source/test/cintltst/cloctst.h b/icu/icu4c/source/test/cintltst/cloctst.h
index af7fa5d06a3..61058e8db15 100644
--- a/icu/icu4c/source/test/cintltst/cloctst.h
+++ b/icu/icu4c/source/test/cintltst/cloctst.h
@@ -142,7 +142,7 @@ static void TestToUnicodeLocaleType(void);
 static void TestToLegacyType(void);
 static void TestBug20149(void);
 static void TestCDefaultLocale(void);
-
+static void TestBug21449InfiniteLoop(void);
 
 /**
  * U_USING_DEFAULT_WARNING