[Bug 47808] New: Cygwin's mintty.exe crashes with a stack overflow

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=47808

Bug ID: 47808
           Summary: Cygwin's mintty.exe crashes with a stack overflow
           Product: Wine
           Version: 4.16
          Hardware: x86-64
               URL: https://cygwin.com/setup-x86_64.exe
                OS: Linux
            Status: NEW
          Keywords: download
          Severity: normal
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 65297
  --> https://bugs.winehq.org/attachment.cgi?id=65297
hack: always expand the stack if within the stack reserve

The problem is that Cygwin replaces the default stack with one that they've
manually allocated, for whatever reason. Unlike Wine's stack, their stack is
actually split into reserved and committed parts.

Then somewhere in gdi32, libfreetype jumps multiple pages of stack at once,
skipping the guard page and triggering a stack overflow. It's within the
reserved portion, but it never touches the guard pages, so we abort
immediately. This is never a problem normally, because Wine commits the whole
stack instead of just part of it.

The architecturally correct way to fix this is normally to have any such
function use _chkstk(). But it's within libfreetype, so that isn't going to
work. The attached patch fixes the bug, but it's probably not correct. I don't
know how much better we can do, though...