Add timeout for fsck on untrusted media

Certain setups of cards can take a long time to fsck.
This adds a timeout to avoid angering the watchdog

Bug: 195615825
Test: Mount removable storage with ~30K folders,
      obeserve timeout in logs
Change-Id: I8b6e2658cf7024645f976599851bbee0557745ca

Utils.cpp

@@ -754,7 +754,53 @@ status_t ForkExecvp(const std::vector<std::string>& args, std::vector<std::strin
     return OK;
 }
 
-pid_t ForkExecvpAsync(const std::vector<std::string>& args) {
+status_t ForkExecvpTimeout(const std::vector<std::string>& args, std::chrono::seconds timeout,
+                           char* context) {
+    int status;
+
+    pid_t wait_timeout_pid = fork();
+    if (wait_timeout_pid == 0) {
+        pid_t pid = ForkExecvpAsync(args, context);
+        if (pid == -1) {
+            _exit(EXIT_FAILURE);
+        }
+        pid_t timer_pid = fork();
+        if (timer_pid == 0) {
+            sleep(timeout.count());
+            _exit(ETIMEDOUT);
+        }
+        if (timer_pid == -1) {
+            PLOG(ERROR) << "fork in ForkExecvpAsync_timeout";
+            kill(pid, SIGTERM);
+            _exit(EXIT_FAILURE);
+        }
+        pid_t finished = wait(&status);
+        if (finished == pid) {
+            kill(timer_pid, SIGTERM);
+        } else {
+            kill(pid, SIGTERM);
+        }
+        if (!WIFEXITED(status)) {
+            _exit(ECHILD);
+        }
+        _exit(WEXITSTATUS(status));
+    }
+    if (waitpid(wait_timeout_pid, &status, 0) == -1) {
+        PLOG(ERROR) << "waitpid in ForkExecvpAsync_timeout";
+        return -errno;
+    }
+    if (!WIFEXITED(status)) {
+        LOG(ERROR) << "Process did not exit normally, status: " << status;
+        return -ECHILD;
+    }
+    if (WEXITSTATUS(status)) {
+        LOG(ERROR) << "Process exited with code: " << WEXITSTATUS(status);
+        return WEXITSTATUS(status);
+    }
+    return OK;
+}
+
+pid_t ForkExecvpAsync(const std::vector<std::string>& args, char* context) {
     auto argv = ConvertToArgv(args);
 
     pid_t pid = fork();
@@ -762,6 +808,12 @@ pid_t ForkExecvpAsync(const std::vector<std::string>& args) {
         close(STDIN_FILENO);
         close(STDOUT_FILENO);
         close(STDERR_FILENO);
+        if (context) {
+            if (setexeccon(context)) {
+                LOG(ERROR) << "Failed to setexeccon in ForkExecvpAsync";
+                abort();
+            }
+        }
 
         execvp(argv[0], const_cast<char**>(argv.data()));
         PLOG(ERROR) << "exec in ForkExecvpAsync";

Utils.h

@@ -37,6 +37,8 @@ namespace vold {
 static const char* kVoldAppDataIsolationEnabled = "persist.sys.vold_app_data_isolation_enabled";
 static const char* kExternalStorageSdcardfs = "external_storage.sdcardfs.enabled";
 
+static constexpr std::chrono::seconds kUntrustedFsckSleepTime(45);
+
 /* SELinux contexts used depending on the block device type */
 extern char* sBlkidContext;
 extern char* sBlkidUntrustedContext;
@@ -106,8 +108,10 @@ status_t ReadMetadataUntrusted(const std::string& path, std::string* fsType, std
 /* Returns either WEXITSTATUS() status, or a negative errno */
 status_t ForkExecvp(const std::vector<std::string>& args,
                     std::vector<std::string>* output = nullptr, char* context = nullptr);
+status_t ForkExecvpTimeout(const std::vector<std::string>& args, std::chrono::seconds timeout,
+                           char* context = nullptr);
 
-pid_t ForkExecvpAsync(const std::vector<std::string>& args);
+pid_t ForkExecvpAsync(const std::vector<std::string>& args, char* context = nullptr);
 
 /* Gets block device size in bytes */
 status_t GetBlockDevSize(int fd, uint64_t* size);

fs/Exfat.cpp

@@ -44,7 +44,7 @@ status_t Check(const std::string& source) {
     cmd.push_back("-y");
     cmd.push_back(source);
 
-    int rc = ForkExecvp(cmd, nullptr, sFsckUntrustedContext);
+    int rc = ForkExecvpTimeout(cmd, kUntrustedFsckSleepTime, sFsckUntrustedContext);
     if (rc == 0) {
         LOG(INFO) << "Check OK";
         return 0;

fs/Vfat.cpp

@@ -68,10 +68,9 @@ status_t Check(const std::string& source) {
         cmd.push_back(source);
 
         // Fat devices are currently always untrusted
-        rc = ForkExecvp(cmd, nullptr, sFsckUntrustedContext);
-
+        rc = ForkExecvpTimeout(cmd, kUntrustedFsckSleepTime, sFsckUntrustedContext);
         if (rc < 0) {
-            LOG(ERROR) << "Filesystem check failed due to logwrap error";
+            LOG(ERROR) << "Filesystem check failed due to fork error";
             errno = EIO;
             return -1;
         }
@@ -81,6 +80,10 @@ status_t Check(const std::string& source) {
                 LOG(INFO) << "Filesystem check completed OK";
                 return 0;
 
+            case 1:
+                LOG(INFO) << "Failed to check filesystem";
+                return -1;
+
             case 2:
                 LOG(ERROR) << "Filesystem check failed (not a FAT filesystem)";
                 errno = ENODATA;
@@ -100,6 +103,11 @@ status_t Check(const std::string& source) {
                 errno = ENODATA;
                 return -1;
 
+            case ETIMEDOUT:
+                LOG(ERROR) << "Filesystem check timed out";
+                errno = ETIMEDOUT;
+                return -1;
+
             default:
                 LOG(ERROR) << "Filesystem check failed (unknown exit code " << rc << ")";
                 errno = EIO;