diff --git a/rpcs3/Emu/Cell/Modules/cellGame.cpp b/rpcs3/Emu/Cell/Modules/cellGame.cpp
index 210cb95bb4..9a246860bc 100644
--- a/rpcs3/Emu/Cell/Modules/cellGame.cpp
+++ b/rpcs3/Emu/Cell/Modules/cellGame.cpp
@@ -150,13 +150,16 @@ error_code cellHddGameCheck(ppu_thread& ppu, u32 version, vm::cptr<char> dirName
 {
 	cellGame.error("cellHddGameCheck(version=%d, dirName=%s, errDialog=%d, funcStat=*0x%x, container=%d)", version, dirName, errDialog, funcStat, container);
 
-	std::string dir = dirName.get_ptr();
-
-	if (dir.size() != 9)
+	if (!dirName || !funcStat || sysutil_check_name_string(dirName.get_ptr(), 1, CELL_GAME_DIRNAME_SIZE) != 0)
 	{
 		return CELL_HDDGAME_ERROR_PARAM;
 	}
 
+	std::string dir = dirName.get_ptr();
+
+	// TODO: Find error code
+	verify(HERE), dir.size() == 9;
+
 	vm::var<CellHddGameCBResult> result;
 	vm::var<CellHddGameStatGet> get;
 	vm::var<CellHddGameStatSet> set;
diff --git a/rpcs3/Emu/Cell/Modules/cellSaveData.cpp b/rpcs3/Emu/Cell/Modules/cellSaveData.cpp
index 2604767043..f5a7303c17 100644
--- a/rpcs3/Emu/Cell/Modules/cellSaveData.cpp
+++ b/rpcs3/Emu/Cell/Modules/cellSaveData.cpp
@@ -240,10 +240,29 @@ static s32 savedata_check_args(u32 operation, u32 version, vm::cptr<char> dirNam
 		return 5;
 	}
 
-	if (operation <= SAVEDATA_OP_AUTO_LOAD && !dirName)
+	if (operation <= SAVEDATA_OP_AUTO_LOAD)
 	{
-		// ****** sysutil savedata parameter error : 2 ******
-		return 2;
+		if (!dirName)
+		{
+			// ****** sysutil savedata parameter error : 2 ******
+			return 2;
+		}
+
+		switch (sysutil_check_name_string(dirName.get_ptr(), 1, CELL_SAVEDATA_DIRNAME_SIZE))
+		{
+		case -1:
+		{
+			// ****** sysutil savedata parameter error : 3 ******
+			return 3;
+		}
+		case -2:
+		{
+			// ****** sysutil savedata parameter error : 4 ******
+			return 4;
+		}
+		case 0: break;
+		default: ASSUME(0);
+		}
 	}
 
 	if ((operation >= SAVEDATA_OP_LIST_AUTO_SAVE && operation <= SAVEDATA_OP_FIXED_LOAD) || operation == SAVEDATA_OP_FIXED_DELETE)
@@ -279,7 +298,50 @@ static s32 savedata_check_args(u32 operation, u32 version, vm::cptr<char> dirNam
 			return 17;
 		}
 
-		// TODO: Theres some check here I've missed about dirNamePrefix
+		char cur, buf[CELL_SAVEDATA_DIRNAME_SIZE + 1]{};
+
+		for (s32 pos = 0, posprefix = 0; cur = setList->dirNamePrefix[pos++], true;)
+		{
+			if (cur == '\0' || cur == '|')
+			{
+				// Check prefix if not empty
+				if (posprefix) 
+				{
+					switch (sysutil_check_name_string(buf, 1, CELL_SAVEDATA_DIRNAME_SIZE))
+					{
+					case -1:
+					{
+						// ****** sysutil savedata parameter error : 16 ******
+						return 16;
+					}
+					case -2:
+					{
+						// ****** sysutil savedata parameter error : 17 ******
+						return 17;
+					}
+					case 0: break;
+					default: ASSUME(0);
+					}
+				}
+
+				if (cur == '\0')
+				{
+					break;
+				}
+
+				// Note: no need to reset buffer, only position
+				posprefix = 0;
+				continue;
+			}
+
+			if (posprefix == CELL_SAVEDATA_DIRNAME_SIZE)
+			{
+				// ****** sysutil savedata parameter error : 17 ******
+				return 17;
+			}
+
+			buf[posprefix++] = cur;
+		}
 
 		if (setList->reserved)
 		{
diff --git a/rpcs3/Emu/Cell/Modules/cellSysCache.cpp b/rpcs3/Emu/Cell/Modules/cellSysCache.cpp
index b9f5cdaa1f..3077f63f2e 100644
--- a/rpcs3/Emu/Cell/Modules/cellSysCache.cpp
+++ b/rpcs3/Emu/Cell/Modules/cellSysCache.cpp
@@ -115,13 +115,13 @@ error_code cellSysCacheMount(vm::ptr<CellSysCacheParam> param)
 
 	const auto cache = g_fxo->get<syscache_info>();
 
-	if (!param || !std::memchr(param->cacheId, '\0', CELL_SYSCACHE_ID_SIZE))
+	if (!param || (param->cacheId[0] && sysutil_check_name_string(param->cacheId, 1, CELL_SYSCACHE_ID_SIZE) != 0))
 	{
 		return CELL_SYSCACHE_ERROR_PARAM;
 	}
 
 	// Full virtualized cache id (with title id included)
-	std::string cache_id = vfs::escape(Emu.GetTitleID() + '_' + param->cacheId, true);
+	std::string cache_id = vfs::escape(Emu.GetTitleID() + '_' + param->cacheId);
 
 	// Full path to virtual cache root (/dev_hdd1)
 	std::string new_path = cache->cache_root + cache_id + '/';
diff --git a/rpcs3/Emu/Cell/Modules/cellSysutil.cpp b/rpcs3/Emu/Cell/Modules/cellSysutil.cpp
index cfc3ffd6d6..e59a93bd32 100644
--- a/rpcs3/Emu/Cell/Modules/cellSysutil.cpp
+++ b/rpcs3/Emu/Cell/Modules/cellSysutil.cpp
@@ -3,6 +3,7 @@
 #include "Emu/IdManager.h"
 #include "Emu/Cell/PPUModule.h"
 
+#include "Emu/Cell/lv2/sys_process.h"
 #include "cellSysutil.h"
 
 #include "Utilities/StrUtil.h"
@@ -134,6 +135,64 @@ void fmt_class_string<CellSysutilParamId>::format(std::string& out, u64 arg)
 	});
 }
 
+// Common string checks used in libsysutil functions
+s32 sysutil_check_name_string(const char* src, s32 minlen, s32 maxlen)
+{
+	s32 lastpos;
+
+	if (g_ps3_process_info.sdk_ver > 0x36FFFF)
+	{
+		// Limit null terminator boundary to before buffer max size
+		lastpos = std::max(maxlen - 1, 0); 
+	}
+	else
+	{
+		// Limit null terminator boundary to one after buffer max size
+		lastpos = maxlen;
+	}
+
+	char cur = src[0];
+
+	if (cur == '_')
+	{
+		// Invalid character at start
+		return -1;
+	}
+
+	for (u32 index = 0;; cur = src[++index])
+	{
+		if (cur == '\0' || index == maxlen)
+		{
+			if (minlen > index || (maxlen == index && src[lastpos]))
+			{
+				// String length is invalid
+				return -2;
+			}
+
+			// OK
+			return 0;
+		}
+
+		if (cur >= 'A' && cur <= 'Z')
+		{
+			continue;
+		}
+
+		if (cur >= '0' && cur <= '9')
+		{
+			continue;
+		}
+
+		if (cur == '-' || cur == '_')
+		{
+			continue;
+		}
+
+		// Invalid character found
+		return -1;
+	}
+}
+
 s32 _cellSysutilGetSystemParamInt()
 {
 	UNIMPLEMENTED_FUNC(cellSysutil);
diff --git a/rpcs3/Emu/Cell/Modules/cellSysutil.h b/rpcs3/Emu/Cell/Modules/cellSysutil.h
index 6015e50b2b..fe5ff892e7 100644
--- a/rpcs3/Emu/Cell/Modules/cellSysutil.h
+++ b/rpcs3/Emu/Cell/Modules/cellSysutil.h
@@ -204,3 +204,4 @@ struct CellSysCacheParam
 
 extern void sysutil_register_cb(std::function<s32(ppu_thread&)>&&);
 extern void sysutil_send_system_cmd(u64 status, u64 param);
+s32 sysutil_check_name_string(const char* src, s32 minlen, s32 maxlen);