linux-kernel - Re: [PATCH v2 19/39] mm/mmap: Add shadow stack pages to memory accounting

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Date:   Tue, 4 Oct 2022 00:32:15 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
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Subject: Re: [PATCH v2 19/39] mm/mmap: Add shadow stack pages to memory
 accounting

On Tue, 2022-10-04 at 03:03 +0300, Kirill A . Shutemov wrote:
> > +     if (vm_flags & VM_SHADOW_STACK)
> > +             return 1;
> > +
> >        return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) ==
> > VM_WRITE;
> 
> Hm. Isn't the last check true for shadow stack too? IIUC, shadow
> stack has
> VM_WRITE set, so accountable_mapping() should work correctly as is.

They are not always VM_WRITE, that can have it removed via mprotect().
But in that case it is just specially tagged read only memory, so
probably isn't accountable. So, yea, I'll remove it. Thanks.