linux-kernel - Re: [PATCH v6 17/20] mm/mmap: Use vms accounted pages in mmap

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Message-ID: <CAHC9VhTWRMKZiximDFAuhY0PwvHt8rk913LLKLQu20tjrnN7cQ@mail.gmail.com>
Date: Wed, 21 Aug 2024 12:35:24 -0400
From: Paul Moore <paul@...l-moore.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Matthew Wilcox <willy@...radead.org>, 
	Vlastimil Babka <vbabka@...e.cz>, sidhartha.kumar@...cle.com, 
	Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>, Kees Cook <kees@...nel.org>, 
	"Paul E . McKenney" <paulmck@...nel.org>, linux-security-module@...r.kernel.org
Subject: Re: [PATCH v6 17/20] mm/mmap: Use vms accounted pages in mmap_region()

On Tue, Aug 20, 2024 at 8:02 PM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>
> Change from nr_pages variable to vms.nr_accounted for the charged pages
> calculation.  This is necessary for a future patch.
>
> This also avoids checking security_vm_enough_memory_mm() if the amount
> of memory won't change.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Cc: Kees Cook <kees@...nel.org>
> Cc: linux-security-module@...r.kernel.org
> Reviewed-by: Kees Cook <kees@...nel.org>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>
> ---
>  mm/mmap.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

I'm pretty sure I already ACK'd this, but I don't see it above so here
it is again:

Acked-by: Paul Moore <paul@...l-moore.com> (LSM)

> diff --git a/mm/mmap.c b/mm/mmap.c
> index 19dac138f913..2a4f1df96f94 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1413,9 +1413,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>          */
>         if (accountable_mapping(file, vm_flags)) {
>                 charged = pglen;
> -               charged -= nr_accounted;
> -               if (security_vm_enough_memory_mm(mm, charged))
> +               charged -= vms.nr_accounted;
> +               if (charged && security_vm_enough_memory_mm(mm, charged))
>                         goto abort_munmap;
> +
>                 vms.nr_accounted = 0;
>                 vm_flags |= VM_ACCOUNT;
>         }
> --
> 2.43.0

-- 
paul-moore.com