ntdll: Temporarily allow KeUserModeCallback calls from client stack.

dlls/ntdll/unix/signal_arm.c

@@ -700,6 +700,14 @@ NTSTATUS WINAPI KeUserModeCallback( ULONG id, const void *args, ULONG len, void
 {
     struct user_callback_frame callback_frame = { { 0 }, ret_ptr, ret_len };
 
+    /* if we have no syscall frame, call the callback directly */
+    if ((char *)&callback_frame < (char *)ntdll_get_thread_data()->kernel_stack ||
+        (char *)&callback_frame > (char *)arm_thread_data()->syscall_frame)
+    {
+        NTSTATUS (WINAPI *func)(const void *, ULONG) = ((void **)NtCurrentTeb()->Peb->KernelCallbackTable)[id];
+        return func( args, len );
+    }
+
     if ((char *)ntdll_get_thread_data()->kernel_stack + min_kernel_stack > (char *)&callback_frame)
         return STATUS_STACK_OVERFLOW;
 

dlls/ntdll/unix/signal_arm64.c

@@ -738,6 +738,14 @@ NTSTATUS WINAPI KeUserModeCallback( ULONG id, const void *args, ULONG len, void
 {
     struct user_callback_frame callback_frame = { {{ 0 }}, ret_ptr, ret_len };
 
+    /* if we have no syscall frame, call the callback directly */
+    if ((char *)&callback_frame < (char *)ntdll_get_thread_data()->kernel_stack ||
+        (char *)&callback_frame > (char *)arm64_thread_data()->syscall_frame)
+    {
+        NTSTATUS (WINAPI *func)(const void *, ULONG) = ((void **)NtCurrentTeb()->Peb->KernelCallbackTable)[id];
+        return func( args, len );
+    }
+
     if ((char *)ntdll_get_thread_data()->kernel_stack + min_kernel_stack > (char *)&callback_frame)
         return STATUS_STACK_OVERFLOW;
 

dlls/ntdll/unix/signal_i386.c

@@ -1569,6 +1569,14 @@ NTSTATUS WINAPI KeUserModeCallback( ULONG id, const void *args, ULONG len, void
 {
     struct user_callback_frame callback_frame = { { 0 }, ret_ptr, ret_len };
 
+    /* if we have no syscall frame, call the callback directly */
+    if ((char *)&callback_frame < (char *)ntdll_get_thread_data()->kernel_stack ||
+        (char *)&callback_frame > (char *)x86_thread_data()->syscall_frame)
+    {
+        NTSTATUS (WINAPI *func)(const void *, ULONG) = ((void **)NtCurrentTeb()->Peb->KernelCallbackTable)[id];
+        return func( args, len );
+    }
+
     if ((char *)ntdll_get_thread_data()->kernel_stack + min_kernel_stack > (char *)&callback_frame)
         return STATUS_STACK_OVERFLOW;
 

dlls/ntdll/unix/signal_x86_64.c

@@ -2293,6 +2293,14 @@ NTSTATUS WINAPI KeUserModeCallback( ULONG id, const void *args, ULONG len, void
 {
     struct user_callback_frame callback_frame = { { 0 }, ret_ptr, ret_len };
 
+    /* if we have no syscall frame, call the callback directly */
+    if ((char *)&callback_frame < (char *)ntdll_get_thread_data()->kernel_stack ||
+        (char *)&callback_frame > (char *)amd64_thread_data()->syscall_frame)
+    {
+        NTSTATUS (WINAPI *func)(const void *, ULONG) = ((void **)NtCurrentTeb()->Peb->KernelCallbackTable)[id];
+        return func( args, len );
+    }
+
     if ((char *)ntdll_get_thread_data()->kernel_stack + min_kernel_stack > (char *)&callback_frame)
         return STATUS_STACK_OVERFLOW;
 

include/wine/unixlib.h

@@ -80,6 +80,8 @@ extern void ntdll_set_exception_jmp_buf( __wine_jmp_buf *jmp );
          } \
     } while (0);
 
+NTSTATUS WINAPI KeUserModeCallback( ULONG id, const void *args, ULONG len, void **ret_ptr, ULONG *ret_len );
+
 /* wide char string functions */
 
 static inline size_t ntdll_wcslen( const WCHAR *str )