[Bug 55138] New: msys2: bash.exe is not able to fork/start another process.

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

Bug ID: 55138
           Summary: msys2: bash.exe is not able to fork/start another
                    process.
           Product: Wine
           Version: 8.10
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 74697
  --> https://bugs.winehq.org/attachment.cgi?id=74697
allocation stacks in parent and child bash.exe

This is a followup to bug 47808.
If I understand it right, bug 47808 was primarily about native libraries
getting called at a win32 stack which was not yet committed.
Those native libraries then jumped over the guard page, therefore the stack
got not grown, instead a crash reported.
This aspect was fixed by using the syscall interface and
therefore bug 47808 was closed.

But there is another issue that causes a msys2-forked process crashing,
because after the stack was grown it still misses the PAGE_READWRITE flags.

For this Zeb Figura included in the first attachement to bug 47808
"always expand the stack if within the stack reserve"
a line adding the flags "VPROT_COMMITTED | VPROT_READ | VPROT_WRITE"
to the page that gets the VPROT_GUARD removed in grow_thread_stack.

This modification still enables a forked process to run.

The issue can be reproduced with an unmodified wine by just
- running msys2 bash.exe interactively
- then trying to start e.g. notepad from it.

Attached file shows the stack when the stack gets allocated
- in a working msys2-parent process and
- in a failing msys2-forked child process.

Therefore it looks like the forked stack get really setup differently,
but it is still not clear if or when this memory gets the READ/WRITE
added in native windows.

[Bug 55138] msys2: bash.exe is not able to fork/start another process.

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

Joel Holdsworth  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[e-mail]

[Bug 55138] msys2/bash.exe: is not able to fork/start another process (cygwin/mintty: silently finishes, fails top open window)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

Bernhard Übelacker  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|msys2: bash.exe is not able |msys2/bash.exe: is not able
                   |to fork/start another       |to fork/start another
                   |process.                    |process (cygwin/mintty:
                   |                            |silently finishes, fails
                   |                            |top open window)
           See Also|                            |https://bugs.winehq.org/sho
                   |                            |w_bug.cgi?id=47808

[Bug 55138] msys2/bash.exe: is not able to fork/start another process (cygwin/mintty: silently finishes, fails top open window)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

--- Comment #1 from Bernhard Übelacker  ---
Created attachment 75738
  --> https://bugs.winehq.org/attachment.cgi?id=75738
ntdll: Add read and write to new guard pages.

This makes also cygwin64 mintty silently fail to open the window.

It looks like cygwins child_info_fork::alloc_stack setups the stack with
three guard pages.
This pages end up with vprot bits 0x33 set (read,write,guard,committed).
Below pages stay with having no vprot bits set.

The function grow_thread_stack seems to be able to grow the stack for these
top three pages without problem.
It is able to set vprot bit 0x30 to the next guard page (guard,committed).

Unfortunately on the next grow_thread_stack it changes the
vprot bits to 0x20, and therefore get_unix_prot(0x20) returns prot=0,
therefore the page looses its guard page status, but gets not committed.
(mprotect is called with unix_prot=0)

Attached patch, adds always read,write to guard pages.

[Bug 55138] msys2/bash.exe: is not able to fork/start another process (cygwin/mintty: silently finishes, fails top open window)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

Fabian Maurer  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[e-mail]

[Bug 55138] msys2/bash.exe: is not able to fork/start another process (cygwin/mintty: silently finishes, fails top open window)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

Bernhard Übelacker  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #75738|0                           |1
        is obsolete|                            |

--- Comment #2 from Bernhard Übelacker  ---
Created attachment 76702
  --> https://bugs.winehq.org/attachment.cgi?id=76702
ntdll: Add read and write to new guard pages. (rebased wine-9.12)

Still present with wine-9.11.

Test was done with a wine tree including patches related to bug 52105.

[Bug 55138] msys2/bash.exe: is not able to fork/start another process (cygwin/mintty: silently finishes, fails top open window)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

Bernhard Übelacker  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |download, source

[Bug 55138] msys2/bash.exe: is not able to fork/start another process (cygwin/mintty: silently finishes, fails top open window)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=55138

[e-mail] changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[e-mail]