From 36f53993418ed77f323995a7421260326923bb25 Mon Sep 17 00:00:00 2001
From: Tom Cherry <tomcherry@google.com>
Date: Wed, 6 Sep 2017 10:07:37 -0700
Subject: [PATCH] logd: handle uidToName() directly

uidToName() originally used a separate worker thread with additional
group permissions.  Threads are not security boundaries however, so
these group permissions are removed in a previous change.

This change handles the lookup for uidToName() directly without using
a separate thread.

Test: boot CF, logd unit tests
Change-Id: If245388bc221bc77102a0bbcee82c8f42b140760
---
 logd/main.cpp | 69 ++++++++++++++++-----------------------------------
 1 file changed, 21 insertions(+), 48 deletions(-)

diff --git a/logd/main.cpp b/logd/main.cpp
index 28dcc5ab7..23bbf864d 100644
--- a/logd/main.cpp
+++ b/logd/main.cpp
@@ -150,43 +150,14 @@ void android::prdebug(const char* fmt, ...) {
     }
 }
 
-static sem_t uidName;
-static uid_t uid;
-static char* name;
-
 static sem_t reinit;
 static bool reinit_running = false;
 static LogBuffer* logBuf = nullptr;
 
-static bool package_list_parser_cb(pkg_info* info, void* /* userdata */) {
-    bool rc = true;
-    if (info->uid == uid) {
-        name = strdup(info->name);
-        // false to stop processing
-        rc = false;
-    }
-
-    packagelist_free(info);
-    return rc;
-}
-
 static void* reinit_thread_start(void* /*obj*/) {
     prctl(PR_SET_NAME, "logd.daemon");
 
     while (reinit_running && !sem_wait(&reinit) && reinit_running) {
-        // uidToName Privileged Worker
-        if (uid) {
-            name = nullptr;
-
-            // if we got the perms wrong above, this would spam if we reported
-            // problems with acquisition of an uid name from the packages.
-            (void)packagelist_parse(package_list_parser_cb, nullptr);
-
-            uid = 0;
-            sem_post(&uidName);
-            continue;
-        }
-
         if (fdDmesg >= 0) {
             static const char reinit_message[] = { KMSG_PRIORITY(LOG_INFO),
                                                    'l',
@@ -223,26 +194,30 @@ static void* reinit_thread_start(void* /*obj*/) {
     return nullptr;
 }
 
-static sem_t sem_name;
-
 char* android::uidToName(uid_t u) {
-    if (!u || !reinit_running) {
-        return nullptr;
-    }
+    struct Userdata {
+        uid_t uid;
+        char* name;
+    } userdata = {
+            .uid = u,
+            .name = nullptr,
+    };
 
-    sem_wait(&sem_name);
+    packagelist_parse(
+            [](pkg_info* info, void* callback_parameter) {
+                auto userdata = reinterpret_cast<Userdata*>(callback_parameter);
+                bool result = true;
+                if (info->uid == userdata->uid) {
+                    userdata->name = strdup(info->name);
+                    // false to stop processing
+                    result = false;
+                }
+                packagelist_free(info);
+                return result;
+            },
+            &userdata);
 
-    // Not multi-thread safe, we use sem_name to protect
-    uid = u;
-
-    name = nullptr;
-    sem_post(&reinit);
-    sem_wait(&uidName);
-    char* ret = name;
-
-    sem_post(&sem_name);
-
-    return ret;
+    return userdata.name;
 }
 
 // Serves as a global method to trigger reinitialization
@@ -363,8 +338,6 @@ int main(int argc, char* argv[]) {
 
     // Reinit Thread
     sem_init(&reinit, 0, 0);
-    sem_init(&uidName, 0, 0);
-    sem_init(&sem_name, 0, 1);
     pthread_attr_t attr;
     if (!pthread_attr_init(&attr)) {
         struct sched_param param;