[PATCH v4 1/2] kernelbase: Allow WriteProcessMemory to succeed on PAGE_EXECUTE and PAGE_EXECUTE_READ.

[Marc-Aurel Zent]

From: Marc-Aurel Zent

---
 dlls/kernel32/tests/virtual.c | 13 +++++++++++++
 dlls/kernelbase/memory.c      | 29 ++++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/dlls/kernel32/tests/virtual.c b/dlls/kernel32/tests/virtual.c
index a023104ad88..3c362b60ae3 100644
--- a/dlls/kernel32/tests/virtual.c
+++ b/dlls/kernel32/tests/virtual.c
@@ -83,6 +83,8 @@ static void test_VirtualAllocEx(void)
     DWORD old_prot;
     MEMORY_BASIC_INFORMATION info;
     HANDLE hProcess;
+    NTSTATUS status;
+    NTSTATUS (NTAPI *pNtWriteVirtualMemory)(HANDLE, void *, const void *, SIZE_T, SIZE_T *);

/* Same process */
     addr1 = VirtualAllocEx(GetCurrentProcess(), NULL, alloc_size, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
@@ -122,6 +124,17 @@ static void test_VirtualAllocEx(void)
     b = ReadProcessMemory(hProcess, addr1, src, 0, &bytes_read);
     ok(b && !bytes_read, "read failed: %lu\n", GetLastError());

+    /* test write to read-only execute region */
+    addr2 = VirtualAllocEx(hProcess, NULL, alloc_size, MEM_COMMIT,
+                           PAGE_EXECUTE_READ);
+    ok(addr2 != NULL, "VirtualAllocEx error %lu\n", GetLastError());
+    b = WriteProcessMemory(hProcess, addr2, src, alloc_size, &bytes_written);
+    ok(b, "WriteProcessMemory should succeed on a PAGE_EXECUTE_READ region. Failed error: %lu\n", GetLastError());
+    pNtWriteVirtualMemory = (NTSTATUS (NTAPI *)(HANDLE, void *, const void *, SIZE_T, SIZE_T *))
+        GetProcAddress(GetModuleHandleW(L"ntdll"), "NtWriteVirtualMemory");
+    status = pNtWriteVirtualMemory(hProcess, addr2, src, alloc_size, &bytes_written);
+    ok(!NT_SUCCESS(status), "Expected NtWriteVirtualMemory to fail on PAGE_EXECUTE_READ, but got status: %lu\n", status);
+
     /* test invalid source buffers */

b = VirtualProtect( src + 0x2000, 0x2000, PAGE_NOACCESS, &old_prot );
diff --git a/dlls/kernelbase/memory.c b/dlls/kernelbase/memory.c
index 4f4bba9a13b..656fd5144b6 100644
--- a/dlls/kernelbase/memory.c
+++ b/dlls/kernelbase/memory.c
@@ -537,7 +537,34 @@ BOOL WINAPI DECLSPEC_HOTPATCH VirtualUnlock( void *addr, SIZE_T size )
 BOOL WINAPI DECLSPEC_HOTPATCH WriteProcessMemory( HANDLE process, void *addr, const void *buffer,
                                                   SIZE_T size, SIZE_T *bytes_written )
 {
-    return set_ntstatus( NtWriteVirtualMemory( process, addr, buffer, size, bytes_written ));
+    NTSTATUS status, protect_status;
+    SIZE_T region_size = size;
+    ULONG old_prot;
+    void *base_addr = addr;
+
+    status = NtWriteVirtualMemory( process, addr, buffer, size, bytes_written );
+
+    if (NT_SUCCESS(status)) 
+    {
+        return set_ntstatus( status );
+    }
+
+    /* In the non-writeable code region case, Windows changes the protection to facilitate the write
+     * and then changes it back. */
+
+    protect_status = NtProtectVirtualMemory( process, &base_addr, &region_size, PAGE_EXECUTE_READWRITE, &old_prot );
+    if (!NT_SUCCESS(protect_status)) return set_ntstatus( protect_status );
+
+    if ((old_prot & PAGE_EXECUTE) == PAGE_EXECUTE ||
+        (old_prot & PAGE_EXECUTE_READ) == PAGE_EXECUTE_READ)
+    {
+        status = NtWriteVirtualMemory( process, addr, buffer, size, bytes_written );
+    }
+
+    protect_status = NtProtectVirtualMemory( process, &base_addr, &region_size, old_prot, &old_prot );
+    if (!NT_SUCCESS(protect_status)) return set_ntstatus( protect_status );
+
+    return set_ntstatus( status );
 }