Re: [PATCH 2/5] sysctl: remove useless ctl_table->parent field

[ebiederm@xmission.com (Eric W. Biederman)]

Lucian Adrian Grijincu <lucian.grijincu@gmail.com> writes:

> The 'parent' field was added for selinux in:
>     commit d912b0cc1a617d7c590d57b7ea971d50c7f02503
>     [PATCH] sysctl: add a parent entry to ctl_table and set the parent entry
>
> and then was used for sysctl_check_table.
>
> Both of the users have found other implementations.

This seems reasonable but we need to be careful in how we merge this so
the individual trees are correct.

> CC: Eric W. Biederman <ebiederm@xmission.com>
> Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
> ---
>  include/linux/sysctl.h |    1 -
>  kernel/sysctl.c        |   11 -----------
>  kernel/sysctl_check.c  |    4 ++--
>  3 files changed, 2 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index 7bb5cb6..1f1da4b 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -1018,7 +1018,6 @@ struct ctl_table
>  	int maxlen;
>  	mode_t mode;
>  	struct ctl_table *child;
> -	struct ctl_table *parent;	/* Automatically set */
>  	proc_handler *proc_handler;	/* Callback for text formatting */
>  	void *extra1;
>  	void *extra2;
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 56f6fc1..42025ec 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1695,18 +1695,8 @@ int sysctl_perm(struct ctl_table_root *root, struct ctl_table *table, int op)
>  	return test_perm(mode, op);
>  }
>  
> -static void sysctl_set_parent(struct ctl_table *parent, struct ctl_table *table)
> -{
> -	for (; table->procname; table++) {
> -		table->parent = parent;
> -		if (table->child)
> -			sysctl_set_parent(table, table->child);
> -	}
> -}
> -
>  static __init int sysctl_init(void)
>  {
> -	sysctl_set_parent(NULL, root_table);
>  #ifdef CONFIG_SYSCTL_SYSCALL_CHECK
>  	sysctl_check_table(current->nsproxy, root_table);
>  #endif
> @@ -1864,7 +1854,6 @@ struct ctl_table_header *__register_sysctl_paths(
>  	header->used = 0;
>  	header->unregistering = NULL;
>  	header->root = root;
> -	sysctl_set_parent(NULL, header->ctl_table);
>  	header->count = 1;
>  #ifdef CONFIG_SYSCTL_SYSCALL_CHECK
>  	if (sysctl_check_table(namespaces, header->ctl_table)) {
> diff --git a/kernel/sysctl_check.c b/kernel/sysctl_check.c
> index 9b4fecd..b7d9c66 100644
> --- a/kernel/sysctl_check.c
> +++ b/kernel/sysctl_check.c
> @@ -95,8 +95,8 @@ static int __sysctl_check_table(struct nsproxy *namespaces,
>  	for (; table->procname; table++) {
>  		const char *fail = NULL;
>  
> -		if (table->parent) {
> -			if (table->procname && !table->parent->procname)
> +		if (depth != 0) { /* has parent */
> +			if (table->procname && !parents[depth - 1]->procname)
>  				SET_FAIL("Parent without procname");
>  		}
>  		if (!table->procname)