From 5fdc4cc746c97e1068bd5f7f33f4efe5f942e812 Mon Sep 17 00:00:00 2001
From: Jeff Vander Stoep <jeffv@google.com>
Date: Fri, 23 Jun 2017 13:36:13 -0700
Subject: [PATCH] Revert "crash_dump: during early boot, output to kmsg on
 userdebug."

This reverts commit bf2dd482412cb7b93f52d2ed2d9be9a32fa8d2f9.

Addresses:
avc: denied { relabelto } for name="kmsg_debug" dev="tmpfs" ino=10642
scontext=u:r:init:s0 tcontext=u:object_r:device:s0 tclass=chr_file

Bug: 62101480, 35197529
Test: build and boot device. Verify selinux denial no longer occurs.
Change-Id: I28ce16f50eec20ef15c1721f41b66f22a84e7cca
---
 debuggerd/libdebuggerd/utility.cpp | 46 +-----------------------------
 init/Android.mk                    |  2 --
 init/init.cpp                      |  9 ------
 3 files changed, 1 insertion(+), 56 deletions(-)

diff --git a/debuggerd/libdebuggerd/utility.cpp b/debuggerd/libdebuggerd/utility.cpp
index 7f450e6bc..22fde5ea4 100644
--- a/debuggerd/libdebuggerd/utility.cpp
+++ b/debuggerd/libdebuggerd/utility.cpp
@@ -22,22 +22,16 @@
 #include <signal.h>
 #include <string.h>
 #include <sys/ptrace.h>
-#include <sys/uio.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
 #include <string>
 
-#include <android-base/logging.h>
-#include <android-base/properties.h>
 #include <android-base/stringprintf.h>
-#include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <backtrace/Backtrace.h>
 #include <log/log.h>
 
-using android::base::unique_fd;
-
 // Whitelist output desired in the logcat output.
 bool is_allowed_in_logcat(enum logtype ltype) {
   if ((ltype == HEADER)
@@ -48,19 +42,6 @@ bool is_allowed_in_logcat(enum logtype ltype) {
   return false;
 }
 
-static bool should_write_to_kmsg() {
-  // Write to kmsg if tombstoned isn't up, and we're able to do so.
-  if (!android::base::GetBoolProperty("ro.debuggable", false)) {
-    return false;
-  }
-
-  if (android::base::GetProperty("init.svc.tombstoned", "") == "running") {
-    return false;
-  }
-
-  return true;
-}
-
 __attribute__((__weak__, visibility("default")))
 void _LOG(log_t* log, enum logtype ltype, const char* fmt, ...) {
   bool write_to_tombstone = (log->tfd != -1);
@@ -68,7 +49,6 @@ void _LOG(log_t* log, enum logtype ltype, const char* fmt, ...) {
                       && log->crashed_tid != -1
                       && log->current_tid != -1
                       && (log->crashed_tid == log->current_tid);
-  static bool write_to_kmsg = should_write_to_kmsg();
 
   char buf[512];
   va_list ap;
@@ -90,30 +70,6 @@ void _LOG(log_t* log, enum logtype ltype, const char* fmt, ...) {
     if (log->amfd_data != nullptr) {
       *log->amfd_data += buf;
     }
-
-    if (write_to_kmsg) {
-      unique_fd kmsg_fd(open("/dev/kmsg_debug", O_WRONLY | O_APPEND | O_CLOEXEC));
-      if (kmsg_fd.get() >= 0) {
-        // Our output might contain newlines which would otherwise be handled by the android logger.
-        // Split the lines up ourselves before sending to the kernel logger.
-        if (buf[len - 1] == '\n') {
-          buf[len - 1] = '\0';
-        }
-
-        std::vector<std::string> fragments = android::base::Split(buf, "\n");
-        for (const std::string& fragment : fragments) {
-          static constexpr char prefix[] = "<3>DEBUG: ";
-          struct iovec iov[3];
-          iov[0].iov_base = const_cast<char*>(prefix);
-          iov[0].iov_len = strlen(prefix);
-          iov[1].iov_base = const_cast<char*>(fragment.c_str());
-          iov[1].iov_len = fragment.length();
-          iov[2].iov_base = const_cast<char*>("\n");
-          iov[2].iov_len = 1;
-          TEMP_FAILURE_RETRY(writev(kmsg_fd.get(), iov, 3));
-        }
-      }
-    }
   }
 }
 
@@ -249,7 +205,7 @@ void dump_memory(log_t* log, Backtrace* backtrace, uintptr_t addr, const char* f
 }
 
 void read_with_default(const char* path, char* buf, size_t len, const char* default_value) {
-  unique_fd fd(open(path, O_RDONLY | O_CLOEXEC));
+  android::base::unique_fd fd(open(path, O_RDONLY));
   if (fd != -1) {
     int rc = TEMP_FAILURE_RETRY(read(fd.get(), buf, len - 1));
     if (rc != -1) {
diff --git a/init/Android.mk b/init/Android.mk
index 489d0767a..866ea34bb 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -9,14 +9,12 @@ init_options += \
     -DALLOW_LOCAL_PROP_OVERRIDE=1 \
     -DALLOW_PERMISSIVE_SELINUX=1 \
     -DREBOOT_BOOTLOADER_ON_PANIC=1 \
-    -DWORLD_WRITABLE_KMSG=1 \
     -DDUMP_ON_UMOUNT_FAILURE=1
 else
 init_options += \
     -DALLOW_LOCAL_PROP_OVERRIDE=0 \
     -DALLOW_PERMISSIVE_SELINUX=0 \
     -DREBOOT_BOOTLOADER_ON_PANIC=0 \
-    -DWORLD_WRITABLE_KMSG=0 \
     -DDUMP_ON_UMOUNT_FAILURE=0
 endif
 
diff --git a/init/init.cpp b/init/init.cpp
index ee87145c3..9e238d449 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -889,9 +889,6 @@ static void selinux_restore_context() {
     LOG(INFO) << "Running restorecon...";
     selinux_android_restorecon("/dev", 0);
     selinux_android_restorecon("/dev/kmsg", 0);
-    if constexpr (WORLD_WRITABLE_KMSG) {
-        selinux_android_restorecon("/dev/kmsg_debug", 0);
-    }
     selinux_android_restorecon("/dev/socket", 0);
     selinux_android_restorecon("/dev/random", 0);
     selinux_android_restorecon("/dev/urandom", 0);
@@ -997,13 +994,7 @@ int main(int argc, char** argv) {
         setgroups(arraysize(groups), groups);
         mount("sysfs", "/sys", "sysfs", 0, NULL);
         mount("selinuxfs", "/sys/fs/selinux", "selinuxfs", 0, NULL);
-
         mknod("/dev/kmsg", S_IFCHR | 0600, makedev(1, 11));
-
-        if constexpr (WORLD_WRITABLE_KMSG) {
-          mknod("/dev/kmsg_debug", S_IFCHR | 0622, makedev(1, 11));
-        }
-
         mknod("/dev/random", S_IFCHR | 0666, makedev(1, 8));
         mknod("/dev/urandom", S_IFCHR | 0666, makedev(1, 9));