Changeset 78363 in vbox

Timestamp:

May 1, 2019 6:56:33 PM (6 years ago)

Author:

vboxsync

Message:

winnt/vboxsf: Fixed ancient bug in the read code path that used potentially stale file size information to determine EOF and adjust the read, something obviously has not business on the guest side. bugref:9172

File:

• trunk/src/VBox/Additions/WINNT/SharedFolders/driver/file.cpp (modified) (2 diffs)

trunk/src/VBox/Additions/WINNT/SharedFolders/driver/file.cpp

@@ -249 +249 @@
 #ifdef LOG_ENABLED
     BOOLEAN AsyncIo = BooleanFlagOn(RxContext->Flags, RX_CONTEXT_FLAG_ASYNC_OPERATION);
+    LONGLONG FileSize;
+    RxGetFileSizeWithLock((PFCB)capFcb, &FileSize);
 #endif
-    LONGLONG FileSize;
-
-    RxGetFileSizeWithLock((PFCB)capFcb, &FileSize);
 
     Log(("VBOXSF: vbsfReadInternal: AsyncIo = %d, Fcb->FileSize = 0x%RX64\n",
@@ -261 +260 @@
          ByteCount, ByteOffset, FileSize));
 
-/** @todo r=bird: This check is incorrect as we must let the host do these
- * checks with up-to-date end-of-file data.  What we've got cached here is
- * potentially out of date.  (This code is here because someone saw it in some
- * sample, I suspect and didn't quite understand what it was all about.  The
- * thing is that when FCB_STATE_READCACHING_ENABLED is set, the caller
- * already checks and the sample probably wanted to cover its bases.  We,
- * don't want to do that as already explained earlier.) */
-#ifdef FCB_STATE_READCACHING_ENABLED    /* Correct spelling for Vista 6001 SDK. */
-    if (!FlagOn(capFcb->FcbState, FCB_STATE_READCACHING_ENABLED))
-#else
-    if (!FlagOn(capFcb->FcbState, FCB_STATE_READCACHEING_ENABLED))
-#endif
-    {
-        if (ByteOffset >= FileSize)
-        {
-            Log(("VBOXSF: vbsfReadInternal: EOF\n"));
-            return STATUS_END_OF_FILE;
-        }
-
-        if (ByteCount > FileSize - ByteOffset)
-            ByteCount = (ULONG)(FileSize - ByteOffset);
-    }
-
-    /** @todo read 0 bytes == always success? */
-    if (   !BufferMdl
-        || ByteCount == 0)
-    {
-        AssertFailed();
-        return STATUS_INVALID_PARAMETER;
-    }
+    AssertReturn(BufferMdl, STATUS_INVALID_PARAMETER);
+    Assert(ByteCount > 0); /* ASSUME this is taken care of elsewhere already. */
 
     ctx.pClient = &g_SfClient;