Merge branch 'de/zen-service-command' of https://github.ol.epicgames.net/ue-foundation/zen into de/zen-service-command

1 files changed, 15 insertions, 2 deletions

diff --git a/src/zenutil/zenserverprocess.cpp b/src/zenutil/zenserverprocess.cpp
index b36f11741..0409cb976 100644
--- a/src/zenutil/zenserverprocess.cpp
+++ b/src/zenutil/zenserverprocess.cpp
@@ -167,10 +167,23 @@ ZenServerState::Initialize()
 		ThrowLastError("Could not map view of Zen server state");
 	}
 #else
-	int Fd = shm_open("/UnrealEngineZen", O_RDWR | O_CREAT | O_CLOEXEC, 0666);
+	ZEN_INFO("{}", S_IRUSR | S_IWUSR | S_IXUSR);
+	ZEN_INFO("{}", geteuid());
+	int Fd = shm_open("/UnrealEngineZen", O_RDWR | O_CREAT | O_CLOEXEC, geteuid() == 0 ? 0766 : 0666);
 	if (Fd < 0)
 	{
-		ThrowLastError("Could not open a shared memory object");
+		// Work around a potential issue if the service user is changed in certain configurations.
+		// If the sysctl 'fs.protected_regular' is set to 1 or 2 (default on many distros),
+		// we will be unable to open an existing shared memory object created by another user using O_CREAT,
+		// even if we have the correct permissions, or are running as root. If we destroy the existing
+		// shared memory object and retry, we'll be able to get past shm_open() so long as we have
+		// the appropriate permissions to create the shared memory object.
+		shm_unlink("/UnrealEngineZen");
+		Fd = shm_open("/UnrealEngineZen", O_RDWR | O_CREAT | O_CLOEXEC, geteuid() == 0 ? 0766 : 0666);
+		if (Fd < 0)
+		{
+			ThrowLastError("Could not open a shared memory object");
+		}
 	}
 	fchmod(Fd, 0666);
 	void* hMap = (void*)intptr_t(Fd);