Re: [ros-dev] [ros-diffs] [jgardou] 64525: [KERNEL32] - Always allocate a guard page at the bottom of the stack. It doesn't depend on it being reserved or committed, it just has to be here.

[Alex Ionescu]

Hi,
This code changes Windows behavior.
Best regards,
Alex Ionescu
On Sat, Oct 4, 2014 at 1:25 PM, <jgardou(a)svn.reactos.org> wrote:
>   Author: jgardou
>  Date: Sat Oct  4 20:25:35 2014
>  New Revision: 64525
>  URL: http://svn.reactos.org/svn/reactos?rev=64525&view=rev
>  Log:
>  [KERNEL32]
>   - Always allocate a guard page at the bottom of the stack.
>  It doesn't depend on it being reserved or committed, it just has to be
>  here.
>  Modified:
>      trunk/reactos/dll/win32/kernel32/client/utils.c
>  Modified: trunk/reactos/dll/win32/kernel32/client/utils.c
>  URL:
> http://svn.reactos.org/svn/reactos/trunk/reactos/dll/win32/kernel32/client/…
>  ==============================================================================
>  --- trunk/reactos/dll/win32/kernel32/client/utils.c     [iso-8859-1]
>  (original)
>  +++ trunk/reactos/dll/win32/kernel32/client/utils.c     [iso-8859-1] Sat
>  Oct  4 20:25:35 2014
>  @@ -358,7 +358,6 @@
>       NTSTATUS Status;
>       PIMAGE_NT_HEADERS Headers;
>       ULONG_PTR Stack;
>  -    BOOLEAN UseGuard;
>       ULONG PageSize, Dummy, AllocationGranularity;
>       SIZE_T StackReserveHeader, StackCommitHeader, GuardPageSize,
>  GuaranteedStackCommit;
>       DPRINT("BaseCreateStack (hProcess: %p, Max: %lx, Current: %lx)\n",
>  @@ -426,18 +425,6 @@
>       /* Update the Stack Position */
>       Stack += StackReserve - StackCommit;
>  -    /* Check if we will need a guard page */
>  -    if (StackReserve > StackCommit)
>  -    {
>  -        Stack -= PageSize;
>  -        StackCommit += PageSize;
>  -        UseGuard = TRUE;
>  -    }
>  -    else
>  -    {
>  -        UseGuard = FALSE;
>  -    }
>  -
>       /* Allocate memory for the stack */
>       Status = NtAllocateVirtualMemory(hProcess,
>                                        (PVOID*)&Stack,
>  @@ -457,25 +444,21 @@
>       InitialTeb->StackLimit = (PVOID)Stack;
>       /* Create a guard page */
>  -    if (UseGuard)
>  -    {
>  -        /* Set the guard page */
>  -        GuardPageSize = PAGE_SIZE;
>  -        Status = NtProtectVirtualMemory(hProcess,
>  -                                        (PVOID*)&Stack,
>  -                                        &GuardPageSize,
>  -                                        PAGE_GUARD | PAGE_READWRITE,
>  -                                        &Dummy);
>  -        if (!NT_SUCCESS(Status))
>  -        {
>  -            DPRINT1("Failure to set guard page\n");
>  -            return Status;
>  -        }
>  -
>  -        /* Update the Stack Limit keeping in mind the Guard Page */
>  -        InitialTeb->StackLimit =
>  (PVOID)((ULONG_PTR)InitialTeb->StackLimit +
>  -                                         GuardPageSize);
>  -    }
>  +    GuardPageSize = PageSize;
>  +    Status = NtProtectVirtualMemory(hProcess,
>  +                                    (PVOID*)&Stack,
>  +                                    &GuardPageSize,
>  +                                    PAGE_GUARD | PAGE_READWRITE,
>  +                                    &Dummy);
>  +    if (!NT_SUCCESS(Status))
>  +    {
>  +        DPRINT1("Failure to set guard page\n");
>  +        return Status;
>  +    }
>  +
>  +    /* Update the Stack Limit keeping in mind the Guard Page */
>  +    InitialTeb->StackLimit = (PVOID)((ULONG_PTR)InitialTeb->StackLimit +
>  +                                     GuardPageSize);
>       /* We are done! */
>       return STATUS_SUCCESS;
>