linux-kernel - Re: [PATCH v3 09/29] mm: abstract shadow stack vma behind `vma_is_shadow

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Date: Thu, 4 Apr 2024 14:39:20 -0700
From: Deepak Gupta <debug@...osinc.com>
To: David Hildenbrand <david@...hat.com>
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	Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH v3 09/29] mm: abstract shadow stack vma behind
 `vma_is_shadow_stack`

On Thu, Apr 04, 2024 at 09:02:17PM +0200, David Hildenbrand wrote:
>On 04.04.24 01:34, Deepak Gupta wrote:
>>  		}
>>-	} else if (!(vm_flags & VM_READ)) {
>>+	} else if (!(vm_flags & VM_READ) && !vma_is_shadow_stack(vm_flags)) {
>>+	/* reads allowed if its shadow stack vma */
>>  		if (!(gup_flags & FOLL_FORCE))
>>  			return -EFAULT;
>>  		/*
>
>Unless I am missing something, this is not a simple cleanup. It should 
>go into a separate patch with a clearly documented reason for that 
>change.

I tried that here
https://lore.kernel.org/linux-mm/CAKC1njTPBqtsAOn-CWhB+-8FaZ2KWkkz-vRZr7MZq=0yLUdjcQ@mail.gmail.com/T/
But at that time, VM_SHADOW_STACK for riscv meant only VM_WRITE. So I think
there was obvious uneasiness with that part.

Now we have VM_SHADOW_STACK pretty much same for all arches and only 64bit.
I'll try it again as a separate patch.

>
>-- 
>Cheers,
>
>David / dhildenb
>