linux-hardening - Re: [RFC PATCH v2 5/8] mseal: Check seal flag for munmap(2)

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Date: Wed, 18 Oct 2023 12:07:10 -0700
From: Jeff Xu <jeffxu@...gle.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: jeffxu@...omium.org, akpm@...ux-foundation.org, keescook@...omium.org, 
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	dave.hansen@...el.com, luto@...nel.org, linux-hardening@...r.kernel.org
Subject: Re: [RFC PATCH v2 5/8] mseal: Check seal flag for munmap(2)

On Wed, Oct 18, 2023 at 11:27 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Wed, 18 Oct 2023 at 10:14, Jeff Xu <jeffxu@...gle.com> wrote:
> This is simply not up for discussion. Any flag for "ignore sealing" is wrong.
>
> We do have one special "unmap" case, namely "unmap_vmas()' called at
> last mmput() -> __mmput() -> exit_mmap().
>
> And yes, that is called at munmap() time too, but that's after the
> point of no return after we've already removed the vma's from the VM
> lists. So it's long after any error cases have been checked.
>
Ah. I see.
I didn't know there was no legit case, which is what I worried about before.
this flag can be removed.