linux-kernel - Re: [PATCH 6/6] mm: Forbid splitting special mappings

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Date:   Fri, 22 Jan 2021 12:58:58 +0000
From:   Will Deacon <will@...nel.org>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Brian Geffon <bgeffon@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Hugh Dickins <hughd@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Minchan Kim <minchan@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 6/6] mm: Forbid splitting special mappings

On Tue, Oct 13, 2020 at 02:34:16AM +0100, Dmitry Safonov wrote:
> Don't allow splitting of vm_special_mapping's.
> It affects vdso/vvar areas. Uprobes have only one page in xol_area so
> they aren't affected.
> 
> Those restrictions were enforced by checks in .mremap() callbacks.
> Restrict resizing with generic .split() callback.
> 
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
>  arch/arm/kernel/vdso.c    |  9 ---------
>  arch/arm64/kernel/vdso.c  | 41 +++------------------------------------
>  arch/mips/vdso/genvdso.c  |  4 ----
>  arch/s390/kernel/vdso.c   | 11 +----------
>  arch/x86/entry/vdso/vma.c | 17 ----------------
>  mm/mmap.c                 | 12 ++++++++++++
>  6 files changed, 16 insertions(+), 78 deletions(-)

For arm64:

Acked-by: Will Deacon <will@...nel.org>

Will