linux-kernel - Re: [PATCH v2] sysctl: treewide: constify ctl_table

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Date: Sun, 3 Mar 2024 15:34:08 +0100
From: Joel Granados <j.granados@...sung.com>
To: Thomas Weißschuh <linux@...ssschuh.net>
CC: Luis Chamberlain <mcgrof@...nel.org>, Kees Cook <keescook@...omium.org>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH v2] sysctl: treewide: constify
 ctl_table_root::permissions

Hey Thomas

Just to be sure I'm following. This is V2 of "[PATCH] sysctl: treewide:
constify ctl_table_root::set_ownership". Right? I ask, because the
subject changes slightly.

Best

On Fri, Feb 23, 2024 at 04:52:16PM +0100, Thomas Weißschuh wrote:
> The permissions callback is not supposed to modify the ctl_table.
> Enforce this expectation via the typesystem.
> 
> The patch was created with the following coccinelle script:
> 
>   @@
>   identifier func, head, ctl;
>   @@
> 
>   int func(
>     struct ctl_table_header *head,
>   - struct ctl_table *ctl)
>   + const struct ctl_table *ctl)
>   { ... }
> 
> (insert_entry() from fs/proc/proc_sysctl.c is a false-positive)
> 
> The three changed locations were validated through manually inspection
> and compilation.
> 
> In addition a search for '.permissions =' was done over the full tree to
> look for places that were missed by coccinelle.
> None were found.
> 
> This change also is a step to put "struct ctl_table" into .rodata
> throughout the kernel.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
> To: Luis Chamberlain <mcgrof@...nel.org>
> To: Kees Cook <keescook@...omium.org>
> To: Joel Granados <j.granados@...sung.com>
> To: David S. Miller <davem@...emloft.net>
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> 
> Changes in v2:
> - flesh out commit messages
> - Integrate changes to set_ownership and ctl_table_args into a single
>   series
> - Link to v1: https://lore.kernel.org/r/20231226-sysctl-const-permissions-v1-1-5cd3c91f6299@weissschuh.net
> ---
> The patch is meant to be merged via the sysctl tree.
> 
> There is an upcoming series that will introduce a new implementation of
> .permission which would need to be adapted [0].
> The adaption would be trivial as the 'table' parameter also not modified
> there.
> 
> This change was originally part of the sysctl-const series [1].
> To slim down that series and reduce the message load on other
> maintainers to a minimumble, submit this patch on its own.
> 
> [0] https://lore.kernel.org/lkml/20240222160915.315255-1-aleksandr.mikhalitsyn@canonical.com/
> [1] https://lore.kernel.org/lkml/20231204-const-sysctl-v2-2-7a5060b11447@weissschuh.net/
> ---
>  include/linux/sysctl.h | 2 +-
>  ipc/ipc_sysctl.c       | 2 +-
>  kernel/ucount.c        | 2 +-
>  net/sysctl_net.c       | 2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index ee7d33b89e9e..0a55b5aade16 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -207,7 +207,7 @@ struct ctl_table_root {
>  	void (*set_ownership)(struct ctl_table_header *head,
>  			      struct ctl_table *table,
>  			      kuid_t *uid, kgid_t *gid);
> -	int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
> +	int (*permissions)(struct ctl_table_header *head, const struct ctl_table *table);
>  };
>  
>  #define register_sysctl(path, table)	\
> diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
> index 8c62e443f78b..b087787f608f 100644
> --- a/ipc/ipc_sysctl.c
> +++ b/ipc/ipc_sysctl.c
> @@ -190,7 +190,7 @@ static int set_is_seen(struct ctl_table_set *set)
>  	return &current->nsproxy->ipc_ns->ipc_set == set;
>  }
>  
> -static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)
> +static int ipc_permissions(struct ctl_table_header *head, const struct ctl_table *table)
>  {
>  	int mode = table->mode;
>  
> diff --git a/kernel/ucount.c b/kernel/ucount.c
> index 4aa6166cb856..90300840256b 100644
> --- a/kernel/ucount.c
> +++ b/kernel/ucount.c
> @@ -38,7 +38,7 @@ static int set_is_seen(struct ctl_table_set *set)
>  }
>  
>  static int set_permissions(struct ctl_table_header *head,
> -				  struct ctl_table *table)
> +			   const struct ctl_table *table)
>  {
>  	struct user_namespace *user_ns =
>  		container_of(head->set, struct user_namespace, set);
> diff --git a/net/sysctl_net.c b/net/sysctl_net.c
> index 051ed5f6fc93..ba9a49de9600 100644
> --- a/net/sysctl_net.c
> +++ b/net/sysctl_net.c
> @@ -40,7 +40,7 @@ static int is_seen(struct ctl_table_set *set)
>  
>  /* Return standard mode bits for table entry. */
>  static int net_ctl_permissions(struct ctl_table_header *head,
> -			       struct ctl_table *table)
> +			       const struct ctl_table *table)
>  {
>  	struct net *net = container_of(head->set, struct net, sysctls);
>  
> 
> ---
> base-commit: ffd2cb6b718e189e7e2d5d0c19c25611f92e061a
> change-id: 20231226-sysctl-const-permissions-d7cfd02a7637
> 
> Best regards,
> -- 
> Thomas Weißschuh <linux@...ssschuh.net>
> 

-- 

Joel Granados

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