[PATCH] ntdll: Fix overflow if running 32bit app w/ wine64

[Brendan McGrath]

wine64 was using IMAGE_NT_HEADERS to access header information
regardless of the execution type; hence it would use
IMAGE_OPTIONAL_HEADER64 for a 32bit app.

This could result in an overflow and a request to mmap for a huge amount
of memory causing an out of memory error.

This patch ensures IMAGE_OPTIONAL_HEADER32 is used for a 32-bit app
and IMAGE_OPTIONAL_HEADER64 is used for a 64-bit app

Signed-off-by: Brendan McGrath <brendan at redmandi.com>
---

This fix is pretty much a copy and paste of code from server/mapping.c. But I'm
not sure if it is the right way to go. There may already be a sanitized
location for these values available within virtual_alloc_thread_stack
that I just couldn't find. 

 dlls/ntdll/virtual.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/dlls/ntdll/virtual.c b/dlls/ntdll/virtual.c
index af1509eae5d..8acea14af93 100644
--- a/dlls/ntdll/virtual.c
+++ b/dlls/ntdll/virtual.c
@@ -1933,9 +1933,26 @@ NTSTATUS virtual_alloc_thread_stack( TEB *teb, SIZE_T reserve_size, SIZE_T commi
 
     if (!reserve_size || !commit_size)
     {
-        IMAGE_NT_HEADERS *nt = RtlImageNtHeader( NtCurrentTeb()->Peb->ImageBaseAddress );
-        if (!reserve_size) reserve_size = nt->OptionalHeader.SizeOfStackReserve;
-        if (!commit_size) commit_size = nt->OptionalHeader.SizeOfStackCommit;
+        struct nt
+        {
+            DWORD Signature;
+            IMAGE_FILE_HEADER FileHeader;
+            union
+            {
+                IMAGE_OPTIONAL_HEADER32 hdr32;
+                IMAGE_OPTIONAL_HEADER64 hdr64;
+            } opt;
+        };
+
+        struct nt *nt = (struct nt*) RtlImageNtHeader( NtCurrentTeb()->Peb->ImageBaseAddress );
+	if (nt->opt.hdr32.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
+           if (!reserve_size) reserve_size = nt->opt.hdr32.SizeOfStackReserve;
+           if (!commit_size) commit_size = nt->opt.hdr32.SizeOfStackCommit;
+	} else {
+           if (!reserve_size) reserve_size = nt->opt.hdr64.SizeOfStackReserve;
+           if (!commit_size) commit_size = nt->opt.hdr64.SizeOfStackCommit;
+	}
+	TRACE("reserve_size: %lu, commit_size: %lu", reserve_size, commit_size);
     }
 
     size = max( reserve_size, commit_size );
-- 
2.17.1