linux-kernel - Re: [PATCH 2/4] proc/sysctl: add shared variables -1

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Date:   Fri, 15 May 2020 01:06:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Xiaoming Ni <nixiaoming@...wei.com>
Cc:     mcgrof@...nel.org, yzaikin@...gle.com, adobriyan@...il.com,
        mingo@...nel.org, peterz@...radead.org, akpm@...ux-foundation.org,
        yamada.masahiro@...ionext.com, bauerman@...ux.ibm.com,
        gregkh@...uxfoundation.org, skhan@...uxfoundation.org,
        dvyukov@...gle.com, svens@...ckframe.org, joel@...lfernandes.org,
        tglx@...utronix.de, Jisheng.Zhang@...aptics.com, pmladek@...e.com,
        bigeasy@...utronix.de, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, wangle6@...wei.com
Subject: Re: [PATCH 2/4] proc/sysctl: add shared variables -1

On Fri, May 15, 2020 at 12:33:42PM +0800, Xiaoming Ni wrote:
> Add the shared variable SYSCTL_NEG_ONE to replace the variable neg_one
> used in both sysctl_writes_strict and hung_task_warnings.
> 
> Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
> ---
>  fs/proc/proc_sysctl.c     | 2 +-
>  include/linux/sysctl.h    | 1 +
>  kernel/hung_task_sysctl.c | 3 +--
>  kernel/sysctl.c           | 3 +--

How about doing this refactoring in advance of the extraction patch?

>  4 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index b6f5d45..acae1fa 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -23,7 +23,7 @@
>  static const struct inode_operations proc_sys_dir_operations;
>  
>  /* shared constants to be used in various sysctls */
> -const int sysctl_vals[] = { 0, 1, INT_MAX };
> +const int sysctl_vals[] = { 0, 1, INT_MAX, -1 };
>  EXPORT_SYMBOL(sysctl_vals);
>  
>  /* Support for permanently empty directories */
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index 02fa844..6d741d6 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -41,6 +41,7 @@
>  #define SYSCTL_ZERO	((void *)&sysctl_vals[0])
>  #define SYSCTL_ONE	((void *)&sysctl_vals[1])
>  #define SYSCTL_INT_MAX	((void *)&sysctl_vals[2])
> +#define SYSCTL_NEG_ONE	((void *)&sysctl_vals[3])

Nit: let's keep these value-ordered? i.e. -1, 0, 1, INT_MAX.

-- 
Kees Cook