From 0d847fb4cb6e219f210689051dc4bd6c0dc120a0 Mon Sep 17 00:00:00 2001
From: Tom Cherry <tomcherry@google.com>
Date: Tue, 4 Aug 2020 17:41:47 -0700
Subject: [PATCH] liblog: add a timeout for logd command socket operations

Add a 2s timeout for logd command socket operations:
  android_logger_clear
  android_logger_get_log_readable_size
  android_logger_get_log_size
  android_logger_set_log_size
  android_logger_get_statistics
  android_logger_get_prune_list
  android_logger_set_prune_list

That correspond to:
  logcat -c
  logcat -g
  logcat -G
  logcat -S
  logcat -p
  logcat -P

These operations should return immediately in typical circumstances,
but if logd is stuck, they would otherwise block indefinitely.  This
allows the commands to gracefully timeout instead.

Test: kill -s STOP `pidof logd`; logcat -g (and other options)
      times out appropriately
Test: logcat -g (and other options) work successfully otherwise
Change-Id: I6c4671a9b3daa4a454c0a14ae7d0b7d3b08be77a
---
 liblog/logd_reader.cpp | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/liblog/logd_reader.cpp b/liblog/logd_reader.cpp
index 82ed6b2b5..7123f602a 100644
--- a/liblog/logd_reader.cpp
+++ b/liblog/logd_reader.cpp
@@ -41,7 +41,7 @@
 
 // Connects to /dev/socket/<name> and returns the associated fd or returns -1 on error.
 // O_CLOEXEC is always set.
-static int socket_local_client(const std::string& name, int type) {
+static int socket_local_client(const std::string& name, int type, bool timeout) {
   sockaddr_un addr = {.sun_family = AF_LOCAL};
 
   std::string path = "/dev/socket/" + name;
@@ -55,6 +55,18 @@ static int socket_local_client(const std::string& name, int type) {
     return -1;
   }
 
+  if (timeout) {
+    // Sending and receiving messages should be instantaneous, but we don't want to wait forever if
+    // logd is hung, so we set a gracious 2s timeout.
+    struct timeval t = {2, 0};
+    if (setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &t, sizeof(t)) == -1) {
+      return -1;
+    }
+    if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &t, sizeof(t)) == -1) {
+      return -1;
+    }
+  }
+
   if (connect(fd, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) == -1) {
     close(fd);
     return -1;
@@ -69,7 +81,7 @@ ssize_t SendLogdControlMessage(char* buf, size_t buf_size) {
   size_t len;
   char* cp;
   int errno_save = 0;
-  int sock = socket_local_client("logd", SOCK_STREAM);
+  int sock = socket_local_client("logd", SOCK_STREAM, true);
   if (sock < 0) {
     return sock;
   }
@@ -268,7 +280,7 @@ static int logdOpen(struct logger_list* logger_list) {
     return sock;
   }
 
-  sock = socket_local_client("logdr", SOCK_SEQPACKET);
+  sock = socket_local_client("logdr", SOCK_SEQPACKET, false);
   if (sock <= 0) {
     if ((sock == -1) && errno) {
       return -errno;