Re: [PATCH 09/12] sysctl: move cad_pid into kernel/pid.c

[Kees Cook <kees@kernel.org>]

On Fri, May 09, 2025 at 02:54:13PM +0200, Joel Granados wrote:
> Move cad_pid as well as supporting function proc_do_cad_pid into
> kernel/pic.c. Replaced call to __do_proc_dointvec with proc_dointvec
> inside proc_do_cad_pid which requires the copy of the ctl_table to
> handle the temp value.
> 
> This is part of a greater effort to move ctl tables into their
> respective subsystems which will reduce the merge conflicts in
> kernel/sysctl.c.
> 
> Signed-off-by: Joel Granados <joel.granados@kernel.org>
> ---
>  kernel/pid.c    | 32 ++++++++++++++++++++++++++++++++
>  kernel/sysctl.c | 31 -------------------------------
>  2 files changed, 32 insertions(+), 31 deletions(-)
> 
> diff --git a/kernel/pid.c b/kernel/pid.c
> index 4ac2ce46817fdefff8888681bb5ca3f2676e8add..bc87ba08ae8b7c67f3457b31309b56b5d90f8c52 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -717,6 +717,29 @@ static struct ctl_table_root pid_table_root = {
>  	.set_ownership	= pid_table_root_set_ownership,
>  };
>  
> +static int proc_do_cad_pid(const struct ctl_table *table, int write, void *buffer,
> +		size_t *lenp, loff_t *ppos)
> +{
> +	struct pid *new_pid;
> +	pid_t tmp_pid;
> +	int r;
> +	struct ctl_table tmp_table = *table;
> +
> +	tmp_pid = pid_vnr(cad_pid);
> +	tmp_table.data = &tmp_pid;
> +
> +	r = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
> +	if (r || !write)
> +		return r;
> +
> +	new_pid = find_get_pid(tmp_pid);
> +	if (!new_pid)
> +		return -ESRCH;
> +
> +	put_pid(xchg(&cad_pid, new_pid));
> +	return 0;
> +}
> +
>  static const struct ctl_table pid_table[] = {
>  	{
>  		.procname	= "pid_max",
> @@ -727,6 +750,15 @@ static const struct ctl_table pid_table[] = {
>  		.extra1		= &pid_max_min,
>  		.extra2		= &pid_max_max,
>  	},
> +#ifdef CONFIG_PROC_SYSCTL
> +	{
> +		.procname	= "cad_pid",
> +		.data		= NULL,

nit: this is redundant, any unspecified member will be zero-initialized.

Regardless:

Reviewed-by: Kees Cook <kees@kernel.org>


> +		.maxlen		= sizeof(int),
> +		.mode		= 0600,
> +		.proc_handler	= proc_do_cad_pid,
> +	},
> +#endif
>  };
>  #endif
>  
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 9d8db9cef11122993d850ab5c753e3da1cbfb5cc..d5bebdd02cd4f1def7d9dd2b85454a9022b600b7 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1224,28 +1224,6 @@ int proc_dointvec_ms_jiffies(const struct ctl_table *table, int write, void *buf
>  				do_proc_dointvec_ms_jiffies_conv, NULL);
>  }
>  
> -static int proc_do_cad_pid(const struct ctl_table *table, int write, void *buffer,
> -		size_t *lenp, loff_t *ppos)
> -{
> -	struct pid *new_pid;
> -	pid_t tmp;
> -	int r;
> -
> -	tmp = pid_vnr(cad_pid);
> -
> -	r = __do_proc_dointvec(&tmp, table, write, buffer,
> -			       lenp, ppos, NULL, NULL);
> -	if (r || !write)
> -		return r;
> -
> -	new_pid = find_get_pid(tmp);
> -	if (!new_pid)
> -		return -ESRCH;
> -
> -	put_pid(xchg(&cad_pid, new_pid));
> -	return 0;
> -}
> -
>  /**
>   * proc_do_large_bitmap - read/write from/to a large bitmap
>   * @table: the sysctl table
> @@ -1541,15 +1519,6 @@ static const struct ctl_table kern_table[] = {
>  		.mode		= 0644,
>  		.proc_handler	= proc_dostring,
>  	},
> -#endif
> -#ifdef CONFIG_PROC_SYSCTL
> -	{
> -		.procname	= "cad_pid",
> -		.data		= NULL,
> -		.maxlen		= sizeof (int),
> -		.mode		= 0600,
> -		.proc_handler	= proc_do_cad_pid,
> -	},
>  #endif
>  	{
>  		.procname	= "overflowuid",
> 
> -- 
> 2.47.2
> 
> 

-- 
Kees Cook