commit acd7b7b0c037b1f7e5feaf8c33e08ea88a071b38
author Ben Fennema <fennema@google.com> Thu Jun 22 15:15:56 2017 -0700
committer Ben Fennema <fennema@google.com> Mon Jun 26 14:13:52 2017 -0700
tree 695d1254d3c6bcf07a07812b29c122e499e029f5
parent 75752c19114b1aeed16d99bc817b9477ccb15098

libcutils: fs_config: fix "system/<partition>/" aliasing

Pull prefix checking into fs_config_cmp and make prefix_cmp be a
glorified partial ? strncmp() : strcmp()

Results before:
[ RUN      ] fs_config.system_alias

[ ERROR ] system/core/libcutils/tests/fs_config.cpp:143:: vendor/lib/hw didn't match system/vendor/lib

[ ERROR ] system/core/libcutils/tests/fs_config.cpp:143:: system/vendor/bin/wifi didn't match vendor/bin/wifi

[ ERROR ] system/core/libcutils/tests/fs_config.cpp:143:: system/odm/bin/wifi didn't match odm/bin/wifi

[ ERROR ] system/core/libcutils/tests/fs_config.cpp:143:: system/oem/bin/wifi didn't match oem/bin/wifi
system/core/libcutils/tests/fs_config.cpp:247: Failure
Value of: check_fs_config_cmp(fs_config_cmp_tests)
  Actual: true
Expected: false
[  FAILED  ] fs_config.system_alias (6 ms)

Results after:
[ RUN      ] fs_config.system_alias
[       OK ] fs_config.system_alias (0 ms)

Bug: 62204623
Test: gTest libcutils-unit-test --gtest_filter=fs_config.*
Change-Id: I8282827002816e86ea3014fed29eabf43b837815
Signed-off-by: Ben Fennema <fennema@google.com>

libcutils/fs_config.cpp

diff --git a/libcutils/fs_config.cpp b/libcutils/fs_config.cpp
index 919b65b..13c4abf 100644
--- a/libcutils/fs_config.cpp
+++ b/libcutils/fs_config.cpp
@@ -266,14 +266,27 @@
     return false;
 }
 
+static inline bool prefix_cmp(bool partial, const char* prefix, size_t len, const char* path,
+                              size_t plen) {
+    return ((partial && plen >= len) || (plen == len)) && !strncmp(prefix, path, len);
+}
+
 // alias prefixes of "<partition>/<stuff>" to "system/<partition>/<stuff>" or
 // "system/<partition>/<stuff>" to "<partition>/<stuff>"
-static bool prefix_cmp(const char* prefix, const char* path, size_t len) {
-    if (!strncmp(prefix, path, len)) return true;
+static bool fs_config_cmp(bool partial, const char* prefix, size_t len, const char* path,
+                          size_t plen) {
+    // If name ends in * then allow partial matches.
+    if (!partial && prefix[len - 1] == '*') {
+        len--;
+        partial = true;
+    }
+
+    if (prefix_cmp(partial, prefix, len, path, plen)) return true;
 
     static const char system[] = "system/";
     if (!strncmp(path, system, strlen(system))) {
         path += strlen(system);
+        plen -= strlen(system);
     } else if (len <= strlen(system)) {
         return false;
     } else if (strncmp(prefix, system, strlen(system))) {
@@ -282,25 +295,11 @@
         prefix += strlen(system);
         len -= strlen(system);
     }
-    return is_partition(prefix, len) && !strncmp(prefix, path, len);
+    return is_partition(prefix, len) && prefix_cmp(partial, prefix, len, path, plen);
 }
-
-static bool fs_config_cmp(bool dir, const char* prefix, size_t len, const char* path, size_t plen) {
-    if (dir) {
-        if (plen < len) {
-            return false;
-        }
-    } else {
-        // If name ends in * then allow partial matches.
-        if (prefix[len - 1] == '*') {
-            return prefix_cmp(prefix, path, len - 1);
-        }
-        if (plen != len) {
-            return false;
-        }
-    }
-    return prefix_cmp(prefix, path, len);
-}
+#ifndef __ANDROID_VNDK__
+auto __for_testing_only__fs_config_cmp = fs_config_cmp;
+#endif
 
 void fs_config(const char* path, int dir, const char* target_out_path, unsigned* uid, unsigned* gid,
                unsigned* mode, uint64_t* capabilities) {