linux-kernel - Re: [PATCH v3 3/4] mm: move dup

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Message-ID: <202504290954.754D25567A@keescook>
Date: Tue, 29 Apr 2025 09:54:14 -0700
From: Kees Cook <kees@...nel.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
	Pedro Falcato <pfalcato@...e.de>,
	David Hildenbrand <david@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Suren Baghdasaryan <surenb@...gle.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] mm: move dup_mmap() to mm

On Mon, Apr 28, 2025 at 04:28:16PM +0100, Lorenzo Stoakes wrote:
> This is a key step in our being able to abstract and isolate VMA allocation
> and destruction logic.
> 
> This function is the last one where vm_area_free() and vm_area_dup() are
> directly referenced outside of mmap, so having this in mm allows us to
> isolate these.
> 
> We do the same for the nommu version which is substantially simpler.
> 
> We place the declaration for dup_mmap() in mm/internal.h and have
> kernel/fork.c import this in order to prevent improper use of this
> functionality elsewhere in the kernel.
> 
> While we're here, we remove the useless #ifdef CONFIG_MMU check around
> mmap_read_lock_maybe_expand() in mmap.c, mmap.c is compiled only if
> CONFIG_MMU is set.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Kees Cook <kees@...nel.org>

-- 
Kees Cook