inc: fsctl: increase request/response size to 16K

dll: remove /Gs[size] switch, fix FspFileSystemResolveReparsePoints to not use more than 4K of stack space

src/dll/fsop.c

@@ -951,7 +951,7 @@ FSP_API NTSTATUS FspFileSystemOpQuerySecurity(FSP_FILE_SYSTEM *FileSystem,
     if (0 == FileSystem->Interface->GetSecurity)
         return STATUS_INVALID_DEVICE_REQUEST;
 
-    SecurityDescriptorSize = FSP_FSCTL_TRANSACT_RSP_SIZEMAX - sizeof *Response;
+    SecurityDescriptorSize = FSP_FSCTL_TRANSACT_RSP_BUFFER_SIZEMAX;
     Result = FileSystem->Interface->GetSecurity(FileSystem, Request,
         (PVOID)USERCONTEXT(Request->Req.QuerySecurity),
         Response->Buffer, &SecurityDescriptorSize);
@@ -989,7 +989,7 @@ FSP_API NTSTATUS FspFileSystemOpQueryStreamInformation(FSP_FILE_SYSTEM *FileSyst
     Result = FileSystem->Interface->GetStreamInfo(FileSystem, Request,
         (PVOID)USERCONTEXT(Request->Req.QueryStreamInformation),
         Response->Buffer,
-        FSP_FSCTL_TRANSACT_RSP_SIZEMAX - sizeof *Response,
+        FSP_FSCTL_TRANSACT_RSP_BUFFER_SIZEMAX,
         &BytesTransferred);
     if (!NT_SUCCESS(Result))
         return Result;
@@ -1088,23 +1088,18 @@ FSP_API BOOLEAN FspFileSystemFindReparsePoint(FSP_FILE_SYSTEM *FileSystem,
     return FALSE;
 }
 
-FSP_API NTSTATUS FspFileSystemResolveReparsePoints(FSP_FILE_SYSTEM *FileSystem,
+FSP_API NTSTATUS FspFileSystemResolveReparsePointsInternal(FSP_FILE_SYSTEM *FileSystem,
     NTSTATUS (*GetReparsePointByName)(
         FSP_FILE_SYSTEM *FileSystem, PVOID Context,
         PWSTR FileName, BOOLEAN IsDirectory, PVOID Buffer, PSIZE_T PSize),
     PVOID Context,
+    PREPARSE_DATA_BUFFER ReparseData, SIZE_T ReparseDataSize0,
     PWSTR FileName, UINT32 ReparsePointIndex, BOOLEAN ResolveLastPathComponent0,
     PIO_STATUS_BLOCK PIoStatus, PVOID Buffer, PSIZE_T PSize)
 {
     PREPARSE_DATA_BUFFER OutputReparseData;
     PWSTR TargetPath, RemainderPath, LastPathComponent, NewRemainderPath, ReparseTargetPath;
     WCHAR RemainderChar;
-    union
-    {
-        REPARSE_DATA_BUFFER V;
-        UINT8 B[FSP_FSCTL_TRANSACT_RSP_BUFFER_SIZEMAX];
-    } ReparseDataBuf;
-    PREPARSE_DATA_BUFFER ReparseData = &ReparseDataBuf.V;
     SIZE_T ReparseDataSize, RemainderPathSize, ReparseTargetPathLength;
     BOOLEAN ResolveLastPathComponent;
     ULONG MaxTries = 32;
@@ -1188,7 +1183,7 @@ FSP_API NTSTATUS FspFileSystemResolveReparsePoints(FSP_FILE_SYSTEM *FileSystem,
         }
 
         RemainderChar = *RemainderPath; *RemainderPath = L'\0';
-        ReparseDataSize = sizeof ReparseDataBuf;
+        ReparseDataSize = ReparseDataSize0;
         Result = GetReparsePointByName(FileSystem, Context, TargetPath, '\0' != RemainderChar,
             ReparseData, &ReparseDataSize);
         *RemainderPath = RemainderChar;
@@ -1277,6 +1272,32 @@ reparse_data_exit:
     return STATUS_REPARSE;
 }
 
+FSP_API NTSTATUS FspFileSystemResolveReparsePoints(FSP_FILE_SYSTEM *FileSystem,
+    NTSTATUS (*GetReparsePointByName)(
+        FSP_FILE_SYSTEM *FileSystem, PVOID Context,
+        PWSTR FileName, BOOLEAN IsDirectory, PVOID Buffer, PSIZE_T PSize),
+    PVOID Context,
+    PWSTR FileName, UINT32 ReparsePointIndex, BOOLEAN ResolveLastPathComponent,
+    PIO_STATUS_BLOCK PIoStatus, PVOID Buffer, PSIZE_T PSize)
+{
+    PREPARSE_DATA_BUFFER ReparseData;
+    NTSTATUS Result;
+
+    ReparseData = MemAlloc(FSP_FSCTL_TRANSACT_RSP_BUFFER_SIZEMAX);
+    if (0 == ReparseData)
+        return STATUS_INSUFFICIENT_RESOURCES;
+
+    Result = FspFileSystemResolveReparsePointsInternal(FileSystem,
+        GetReparsePointByName, Context,
+        ReparseData, FSP_FSCTL_TRANSACT_RSP_BUFFER_SIZEMAX,
+        FileName, ReparsePointIndex, ResolveLastPathComponent,
+        PIoStatus, Buffer, PSize);
+
+    MemFree(ReparseData);
+
+    return Result;
+}
+
 FSP_API NTSTATUS FspFileSystemCanReplaceReparsePoint(
     PVOID CurrentReparseData, SIZE_T CurrentReparseDataSize,
     PVOID ReplaceReparseData, SIZE_T ReplaceReparseDataSize)

src/shared/minimal.h

@@ -26,11 +26,10 @@
  * - "C/C++ > Code Generation > Basic Runtime Checks" must be set to "Default"
  * - "C/C++ > Code Generation > Runtime Library" must be set to "Multi-threaded (/MT)".
  * - "C/C++ > Code Generation > Security Check" must be disabled (/GS-).
- * - "C/C++ > Command Line > Additional Options" add "/Gs16384" to disable __chkstk probes.
  * - "Linker > Input > Ignore All Default Libraries" must be "Yes".
  *
  *
- * Update:
+ * Update 1:
  *
  * It is possible to have the "Linker > Input > Ignore All Default Libraries"
  * setting to "No" and still eliminate most dependencies on the MSVCRT libraries.
@@ -44,6 +43,22 @@
  * that are not required (or worse create a half-baked CRT). For example, the WinFsp
  * DLL ensures this by setting the "Linker > Input > Ignore All Default Libraries"
  * to "Yes" on 64-bit builds and "No" on 32-bit builds.
+ *
+ *
+ * Update 2:
+ *
+ * Using the /Gs[size] compiler option with a large size is a very bad idea.
+ * Turns out that the compiler uses the _chkstk call to ensure that enough
+ * stack space has been committed even when a function accesses locations in
+ * the stack below the guard page.
+ *
+ * The following links explain the problem very well:
+ * - http://stackoverflow.com/questions/8400118/what-is-the-purpose-of-the-chkstk-function#8400171
+ * - https://support.microsoft.com/en-us/kb/100775
+ *
+ * A library/program that does not wish to use the MSVCRT libraries (and hence
+ * does not have _chkstk available) must take care to not use more than a page
+ * (4096 bytes) of stack within a single function.
  */
 
 #undef RtlFillMemory

src/sys/driver.h

@@ -735,7 +735,7 @@ enum
     FspFsvolDeviceDirInfoCacheCapacity = 100,
     FspFsvolDeviceDirInfoCacheItemSizeMax = FSP_FSCTL_ALIGN_UP(16384, PAGE_SIZE),
     FspFsvolDeviceStreamInfoCacheCapacity = 100,
-    FspFsvolDeviceStreamInfoCacheItemSizeMax = 4096,
+    FspFsvolDeviceStreamInfoCacheItemSizeMax = FSP_FSCTL_ALIGN_UP(16384, PAGE_SIZE),
 };
 typedef struct
 {