From 0d49e87468ebc2ba7b83562e8408ce64dc820bd5 Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Sat, 5 Dec 2015 11:31:51 -0800
Subject: [PATCH] sys: IRP_MJ_CREATE

---
 build/VStudio/winfsp.sln |  3 +++
 src/sys/create.c         | 26 +++++++++++++++++++++-----
 src/sys/driver.h         | 25 +++++++++++++++++++++----
 src/sys/fileobj.c        |  1 +
 4 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/build/VStudio/winfsp.sln b/build/VStudio/winfsp.sln
index 16057469..323f8695 100644
--- a/build/VStudio/winfsp.sln
+++ b/build/VStudio/winfsp.sln
@@ -4,6 +4,9 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 VisualStudioVersion = 14.0.23107.0
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "winfsp.dll", "winfsp_dll.vcxproj", "{4A7C0B21-9E10-4C81-92DE-1493EFCF24EB}"
+	ProjectSection(ProjectDependencies) = postProject
+		{C85C26BA-8C22-4D30-83DA-46C3548E6332} = {C85C26BA-8C22-4D30-83DA-46C3548E6332}
+	EndProjectSection
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "winfsp.sys", "winfsp_sys.vcxproj", "{C85C26BA-8C22-4D30-83DA-46C3548E6332}"
 EndProject
diff --git a/src/sys/create.c b/src/sys/create.c
index 5710cc65..463b487d 100644
--- a/src/sys/create.c
+++ b/src/sys/create.c
@@ -403,7 +403,7 @@ VOID FspFsvolCreateComplete(
     FsContext->UserContext = Response->Rsp.Create.UserContext;
     FileObject->FsContext2 = (PVOID)(UINT_PTR)Response->Rsp.Create.UserContext2;
 
-    /* following must be performed under the fsvol lock */
+    /* lock the file system volume device while accessing its generic table */
     ExAcquireResourceExclusiveLite(&FsvolDeviceExtension->Base.Resource, TRUE);
     try
     {
@@ -415,19 +415,34 @@ VOID FspFsvolCreateComplete(
             Result = STATUS_INSUFFICIENT_RESOURCES;
         else
         {
-            /* do the share access checks */
+            /* share access check */
             if (Inserted)
             {
+                /*
+                 * This is a newly created FsContext. Set its share access and
+                 * increment its open count. There is no need to acquire the
+                 * FsContext's Resource (because it is newly created).
+                 */
                 IoSetShareAccess(DesiredAccess, ShareAccess, FileObject,
                     &FsContext->ShareAccess);
                 FspFileContextOpen(FsContext);
             }
             else
             {
-                Result = IoCheckShareAccess(DesiredAccess, ShareAccess, FileObject,
-                    &FsContext->ShareAccess, TRUE);
+                /*
+                 * This is an existing FsContext. We must acquire its Resource and
+                 * check if there is a delete pending and the share access. Only if
+                 * both tests succeed we increment the open count and report success.
+                 */
+                ExAcquireResourceExclusiveLite(FsContext->Header.Resource, TRUE);
+                if (FsContext->DeletePending)
+                    Result = STATUS_DELETE_PENDING;
+                else
+                    Result = IoCheckShareAccess(DesiredAccess, ShareAccess, FileObject,
+                        &FsContext->ShareAccess, TRUE);
                 if (NT_SUCCESS(Result))
                     FspFileContextOpen(FsContext);
+                ExReleaseResourceLite(FsContext->Header.Resource);
             }
         }
     }
@@ -444,9 +459,10 @@ VOID FspFsvolCreateComplete(
         FSP_RETURN();
     }
 
-    /* does an FsContext with the same UserContext already exist? */
+    /* did an FsContext with the same UserContext already exist? */
     if (!Inserted)
     {
+        /* delete the newly created FsContext and use the existing one */
         FspFileContextDelete(FileObject->FsContext);
         FileObject->FsContext = FsContext;
     }
diff --git a/src/sys/driver.h b/src/sys/driver.h
index a71c9610..0f2c39e2 100644
--- a/src/sys/driver.h
+++ b/src/sys/driver.h
@@ -363,9 +363,13 @@ typedef struct
 {
     FSRTL_ADVANCED_FCB_HEADER Header;
     FSP_FILE_CONTEXT_NONPAGED *NonPaged;
+    /* interlocked access */
+    LONG RefCount;
+    /* protected by Header.Resource */
     LONG OpenCount;
     SHARE_ACCESS ShareAccess;
-        /* protected by containing fsvol lock */
+    BOOLEAN DeletePending;
+    /* read-only after creation */
     UINT64 UserContext;
     UNICODE_STRING FileName;
     WCHAR FileNameBuf[];
@@ -375,13 +379,26 @@ VOID FspFileContextDelete(FSP_FILE_CONTEXT *Context);
 static inline
 VOID FspFileContextOpen(FSP_FILE_CONTEXT *Context)
 {
-    InterlockedIncrement(&Context->OpenCount);
+    ASSERT(0 == Context->OpenCount || ExIsResourceAcquiredExclusiveLite(Context->Header.Resource));
+    Context->OpenCount++;
 }
 static inline
 VOID FspFileContextClose(FSP_FILE_CONTEXT *Context)
 {
-    LONG Result = InterlockedDecrement(&Context->OpenCount);
-    if (0 == Result)
+    ASSERT(ExIsResourceAcquiredExclusiveLite(Context->Header.Resource));
+    ASSERT(0 < Context->OpenCount);
+    Context->OpenCount--;
+}
+static inline
+VOID FspFileContextRetain(FSP_FILE_CONTEXT *Context)
+{
+    InterlockedIncrement(&Context->RefCount);
+}
+static inline
+VOID FspFileContextRelease(FSP_FILE_CONTEXT *Context)
+{
+    LONG RefCount = InterlockedDecrement(&Context->RefCount);
+    if (0 == RefCount)
         FspFileContextDelete(Context);
 }
 
diff --git a/src/sys/fileobj.c b/src/sys/fileobj.c
index cc13d875..eeef9e5f 100644
--- a/src/sys/fileobj.c
+++ b/src/sys/fileobj.c
@@ -46,6 +46,7 @@ NTSTATUS FspFileContextCreate(ULONG ExtraSize, FSP_FILE_CONTEXT **PFsContext)
     FsContext->Header.PagingIoResource = &NonPaged->PagingIoResource;
     FsRtlSetupAdvancedHeader(&FsContext->Header, &NonPaged->HeaderFastMutex);
     FsContext->NonPaged = NonPaged;
+    FsContext->RefCount = 1;
     RtlInitEmptyUnicodeString(&FsContext->FileName, FsContext->FileNameBuf, (USHORT)ExtraSize);
 
     *PFsContext = FsContext;