linux-kernel - Re: [PATCH] arm64/mm: Delete __init region from memblock.reserved

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMj1kXGhiz5SHxABi5UwZvd_Lx-EpvfQ2_isPu-X7jmi3dogdg@mail.gmail.com>
Date: Fri, 30 Aug 2024 10:14:54 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Rong Qianfeng <rongqianfeng@...o.com>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Baoquan He <bhe@...hat.com>, 
	Petr Tesarik <ptesarik@...e.com>, Baruch Siach <baruch@...s.co.il>, 
	"Mike Rapoport (IBM)" <rppt@...nel.org>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, opensource.kernel@...o.com
Subject: Re: [PATCH] arm64/mm: Delete __init region from memblock.reserved

Hi Rong,

On Fri, 30 Aug 2024 at 10:00, Rong Qianfeng <rongqianfeng@...o.com> wrote:
>
> If CONFIG_ARCH_KEEP_MEMBLOCK is enabled, the memory information in
> memblock will be retained. We release the __init memory here, and
> we should also delete the corresponding region in memblock.reserved.
>
> Signed-off-by: Rong Qianfeng <rongqianfeng@...o.com>
> ---
>  arch/arm64/mm/init.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index bfb10969cbf0..99cfa217e905 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -402,6 +402,13 @@ void __init mem_init(void)
>
>  void free_initmem(void)
>  {
> +       if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {

This is always true on arm64

> +               unsigned long aligned_begin = ALIGN_DOWN((u64)__init_begin, PAGE_SIZE);
> +               unsigned long aligned_end = ALIGN((u64)__init_end, PAGE_SIZE);
> +
> +               memblock_free((void *)aligned_begin, aligned_end - aligned_begin);
> +       }
> +

What does this achieve? The memory is already being reused by the page
allocator (due to free_reserved_area()), and the memblock allocator is
no longer usable at this point anyway.

>         free_reserved_area(lm_alias(__init_begin),
>                            lm_alias(__init_end),
>                            POISON_FREE_INITMEM, "unused kernel");