linux-kernel - Re: [PATCH v3 0/9] Support strict kernel memory permissions for security

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Date:   Tue, 31 Mar 2020 22:32:54 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Zong Li <zong.li@...ive.com>
Cc:     palmer@...belt.com, paul.walmsley@...ive.com,
        aou@...s.berkeley.edu, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/9] Support strict kernel memory permissions for
 security

Hi Zong,

On Tue, 10 Mar 2020 00:55:35 +0800
Zong Li <zong.li@...ive.com> wrote:

> The main purpose of this patch series is changing the kernel mapping permission
> , make sure that code is not writeable, data is not executable, and read-only
> data is neither writable nor executable.
> 
> This patch series also supports the relevant implementations such as
> ARCH_HAS_SET_MEMORY, ARCH_HAS_SET_DIRECT_MAP,
> ARCH_SUPPORTS_DEBUG_PAGEALLOC and DEBUG_WX.

The order of the patches seems a bit strange. Since the first 7 patches
makes kernel read-only, at that point ftrace is broken and it is fixed
by the last 2 patches. That is not bisect-friendly. Can you move the
last 2 patches to the top?

Thank you,

> 
> Changes in v3:
>  - Fix build error on nommu configuration. We already support nommu on
>    RISC-V, so we should consider nommu case and test not only rv32/64,
>    but also nommu.
> 
> Changes in v2:
>  - Use _data to specify the start of data section with write permission.
>  - Change ftrace patch text implementaion.
>  - Separate DEBUG_WX patch to another patchset.
> 
> Zong Li (9):
>   riscv: add ARCH_HAS_SET_MEMORY support
>   riscv: add ARCH_HAS_SET_DIRECT_MAP support
>   riscv: add ARCH_SUPPORTS_DEBUG_PAGEALLOC support
>   riscv: move exception table immediately after RO_DATA
>   riscv: add alignment for text, rodata and data sections
>   riscv: add STRICT_KERNEL_RWX support
>   riscv: add macro to get instruction length
>   riscv: introduce interfaces to patch kernel code
>   riscv: patch code by fixmap mapping
> 
>  arch/riscv/Kconfig                  |   6 +
>  arch/riscv/include/asm/bug.h        |   8 ++
>  arch/riscv/include/asm/fixmap.h     |   2 +
>  arch/riscv/include/asm/patch.h      |  12 ++
>  arch/riscv/include/asm/set_memory.h |  48 +++++++
>  arch/riscv/kernel/Makefile          |   4 +-
>  arch/riscv/kernel/ftrace.c          |  13 +-
>  arch/riscv/kernel/patch.c           | 120 ++++++++++++++++++
>  arch/riscv/kernel/traps.c           |   3 +-
>  arch/riscv/kernel/vmlinux.lds.S     |  11 +-
>  arch/riscv/mm/Makefile              |   2 +-
>  arch/riscv/mm/init.c                |  44 +++++++
>  arch/riscv/mm/pageattr.c            | 187 ++++++++++++++++++++++++++++
>  13 files changed, 445 insertions(+), 15 deletions(-)
>  create mode 100644 arch/riscv/include/asm/patch.h
>  create mode 100644 arch/riscv/include/asm/set_memory.h
>  create mode 100644 arch/riscv/kernel/patch.c
>  create mode 100644 arch/riscv/mm/pageattr.c
> 
> -- 
> 2.25.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>