Johannes Brandstätter : ntdll: Check for NULL context in NtGetContextThread.

[Alexandre Julliard]

Module: wine
Branch: stable
Commit: b9e512d2428473bff6bce9a476d76a2b9ddcc3a3
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=b9e512d2428473bff6bce9a47...

Author: Johannes Brandstätter 
Date:   Wed Jul 11 17:45:32 2018 +0200

ntdll: Check for NULL context in NtGetContextThread.

Crash Bandicoot N. Sane Trilogy calls NtGetContextThread
with the context being set to NULL which leads to a crash.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=45428
Signed-off-by: Johannes Brandstätter 
Signed-off-by: Alexandre Julliard 
(cherry picked from commit ec418e7f55f5e38f8825187ae5dfe33fec31689b)
Signed-off-by: Michael Stefaniuc

---

dlls/ntdll/signal_x86_64.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/dlls/ntdll/signal_x86_64.c b/dlls/ntdll/signal_x86_64.c
index 60da3f3..b7e90c5 100644
--- a/dlls/ntdll/signal_x86_64.c
+++ b/dlls/ntdll/signal_x86_64.c
@@ -2137,9 +2137,13 @@ NTSTATUS WINAPI NtSetContextThread( HANDLE handle, const CONTEXT *context )
 NTSTATUS WINAPI NtGetContextThread( HANDLE handle, CONTEXT *context )
 {
     NTSTATUS ret;
-    DWORD needed_flags = context->ContextFlags;
+    DWORD needed_flags;
     BOOL self = (handle == GetCurrentThread());

+    if (!context) return STATUS_INVALID_PARAMETER;
+
+    needed_flags = context->ContextFlags;
+
     /* debug registers require a server call */
     if (context->ContextFlags & (CONTEXT_DEBUG_REGISTERS & ~CONTEXT_AMD64)) self = FALSE;