linux-kernel - Re: [kernel-hardening][PATCH] arm: hw_breakpoint: Mark variables as __ro_after

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Date:   Mon, 11 Dec 2017 11:24:06 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jinbum Park <jinb.park7@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [kernel-hardening][PATCH] arm: hw_breakpoint: Mark variables as __ro_after_init

On Mon, Dec 11, 2017 at 4:50 AM, Jinbum Park <jinb.park7@...il.com> wrote:
> core_num_brps, core_num_wrps, debug_arch, has_ossr,
> max_watchpoint_len are setup once while init stage,
> and never changed after that.
> so it is good candidate for __ro_after_init.
>
> Signed-off-by: Jinbum Park <jinb.park7@...il.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

(Probably good to toss this into the ARM patch tracker.)

-Kees

> ---
>  arch/arm/kernel/hw_breakpoint.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
> index af2a7f1..629e251 100644
> --- a/arch/arm/kernel/hw_breakpoint.c
> +++ b/arch/arm/kernel/hw_breakpoint.c
> @@ -44,17 +44,17 @@
>  static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
>
>  /* Number of BRP/WRP registers on this CPU. */
> -static int core_num_brps;
> -static int core_num_wrps;
> +static int core_num_brps __ro_after_init;
> +static int core_num_wrps __ro_after_init;
>
>  /* Debug architecture version. */
> -static u8 debug_arch;
> +static u8 debug_arch __ro_after_init;
>
>  /* Does debug architecture support OS Save and Restore? */
> -static bool has_ossr;
> +static bool has_ossr __ro_after_init;
>
>  /* Maximum supported watchpoint length. */
> -static u8 max_watchpoint_len;
> +static u8 max_watchpoint_len __ro_after_init;
>
>  #define READ_WB_REG_CASE(OP2, M, VAL)                  \
>         case ((OP2 << 4) + M):                          \
> --
> 1.9.1
>



-- 
Kees Cook
Pixel Security