linux-kernel - Re: [PATCH 4/5] mm/mseal: separate out and simplify VMA gap check

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Message-ID: <ky2jvl6uyi75qwfmpwzmwu6qfnlwxshk2zunywe3pve2pshdxj@p2ihhzov3imx>
Date: Mon, 14 Jul 2025 16:17:23 +0100
From: Pedro Falcato <pfalcato@...e.de>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R . Howlett" <Liam.Howlett@...cle.com>, David Hildenbrand <david@...hat.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Jeff Xu <jeffxu@...omium.org>
Subject: Re: [PATCH 4/5] mm/mseal: separate out and simplify VMA gap check

On Mon, Jul 14, 2025 at 02:00:39PM +0100, Lorenzo Stoakes wrote:
> The check_mm_seal() function is doing something general - checking whether
> a range contains only VMAs (or rather that it does NOT contain any unmapped
> regions).
> 
> Generalise this and put the logic in mm/vma.c - introducing
> range_contains_unmapped(). Additionally we can simplify the logic, we are
> simply checking whether the last vma->vm_end has either a VMA starting
> after it or ends before the end parameter.
>

I don't like this. Unless you have any other user for this in mind,
we'll proliferate this awful behavior (and add this into core vma code).

I have some patches locally to fully remove this upfront check, and AFAIK
we're somewhat in agreement that we can simply nuke this check (for
various reasons, including that we *still* don't have a man page for the
syscall). I can send them for proper discussion after your series lands.

-- 
Pedro