linux-kernel - Re: [PATCH v2] sysctl: treewide: constify the ctl_table argument of proc

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Message-ID: <202406191350.BB98FF1@keescook>
Date: Wed, 19 Jun 2024 13:51:15 -0700
From: Kees Cook <kees@...nel.org>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Joel Granados <j.granados@...sung.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sysctl: treewide: constify the ctl_table argument of
 proc_handlers

On Wed, Jun 19, 2024 at 12:09:00PM +0200, Thomas Weißschuh wrote:
> Adapt the proc_hander function signature to make it clear that handlers
> are not supposed to modify their ctl_table argument.
> 
> This is also a prerequisite to moving the static ctl_table structs into
> read-only data.
> 
> The patch was mostly generated by coccinelle with the following script:
> 
>     @@
>     identifier func, ctl, write, buffer, lenp, ppos;
>     @@
> 
>     int func(
>     - struct ctl_table *ctl,
>     + const struct ctl_table *ctl,
>       int write, void *buffer, size_t *lenp, loff_t *ppos)
>     { ... }
> 
> In addition to the scripted changes some other changes are done:
> 
> * The "typedef proc_handler" in include/linux/sysctl.h is changed to use
>   the "const ctl_table".
> 
> * The prototypes of non-static handlers in header-files are adapted
>   to match the changes of their respective definitions.
> 
> * kernel/watchdog.c: proc_watchdog_common()
>   This is called from a proc_handler itself and is als calling back
>   into another proc_handler, making it necessary to change it as part
>   of the proc_handler migration.
> 
> No functional change.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>

This looks good! I'll be glad to see these all be read-only. :)

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

-- 
Kees Cook