From baec63017990759664ae508e0b9ce342f22fc918 Mon Sep 17 00:00:00 2001
From: Pavel Siska <siska@cesnet.cz>
Date: Mon, 15 Jul 2024 20:26:25 +0200
Subject: [PATCH] appfs - use fusermount3 to unmount the mountPoint fusermount3
 can unmount mountPoint without root priveleges. fusermount3 is called using
 std::system function.

---
 src/appFs/appFs.cpp | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/src/appFs/appFs.cpp b/src/appFs/appFs.cpp
index 6530df6..9705a8e 100644
--- a/src/appFs/appFs.cpp
+++ b/src/appFs/appFs.cpp
@@ -8,11 +8,10 @@
 
 #include <appFs.hpp>
 
+#include <cstdlib>
 #include <cstring>
 #include <filesystem>
 #include <iostream>
-#include <sstream>
-#include <sys/mount.h>
 #include <telemetry.hpp>
 #include <unistd.h>
 
@@ -356,6 +355,23 @@ static void createDirectories(const std::string& path)
 	}
 }
 
+static void fuserUnmount(const std::string& mountPoint)
+{
+	// NOLINTBEGIN (concurrency-mt-unsafe, std::system function is not thread safe)
+	const std::string whichCommand = "which fusermount3 > /dev/null 2>&1";
+	const int ret = std::system(whichCommand.c_str());
+	if (ret != 0) {
+		std::cerr << "fusermount3 is not found. Unable to unmount '" + mountPoint << "'\n";
+		return;
+	}
+
+	const std::string fusermountCommand = "fusermount3 -u " + mountPoint;
+	if (std::system(fusermountCommand.c_str()) != 0) {
+		throw std::runtime_error(fusermountCommand + " has failed.");
+	}
+	// NOLINTEND
+}
+
 class FuseArgs {
 public:
 	FuseArgs()
@@ -389,22 +405,17 @@ AppFsFuse::AppFsFuse(
 	setFuseOperations(&fuseOps);
 
 	/**
-	 * If tryToUnmountOnStart is true, this code attempts to unmount the specified mount point.
-	 * This is necessary because if the application terminates unexpectedly, the filesystem
-	 * might remain mounted, which can prevent proper status checking and cause subsequent
-	 * attempts to mount it to fail. By forcing an unmount here, we ensure the mount point is
-	 * in a clean state before proceeding. If the unmount fails, an exception is thrown to
-	 * indicate that the cleanup process was unsuccessful.
+	 * If tryToUnmountOnStart is true, this code attempts to unmount the specified mount point using
+	 * fusermount3 binary. This is necessary because if the application terminates unexpectedly, the
+	 * filesystem might remain mounted, which can prevent proper status checking and cause
+	 * subsequent attempts to mount it to fail. By forcing an unmount here, we ensure the mount
+	 * point is in a clean state before proceeding.
 	 */
 	if (tryToUnmountOnStart) {
-		const int ret = umount2(mountPoint.c_str(), MNT_FORCE | UMOUNT_NOFOLLOW);
-		if (ret < 0 && errno != ENOENT) { // ENOENT means that No such directory exists
-			throw std::runtime_error(
-				"umount of " + mountPoint + " has failed. Error: " + std::to_string(errno));
-		}
+		fuserUnmount(mountPoint);
 	}
 
-	if (createMountPoint) {
+	if (!createMountPoint) {
 		createDirectories(mountPoint);
 	}