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

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Date: Thu, 20 Jun 2024 16:34:52 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Joel Granados <j.granados@...sung.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Kees Cook <kees@...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 2024-06-20 12:34:51+0000, Joel Granados wrote:
> 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>
> Will test this in 0-day in [1] to avoid potential conflicts with all the
> other stuff going into linux-next and because it does not apply cleanly to
> sysctl-next. Don't expect any issues from 0-day as it is a
> non-functional trivial change.

Thanks!

> I'll use this patch as is when the time comes during the end of the
> merge window (at that point it should apply cleanly) and go into 
> 
> @Thomas: Can I ping you during the merge window to double check that
> there are no additional proc_handlers (without the const argument)
> that might not be present in today's linux-next?

Sure, I'll test it from time to time anyways.

> Best
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/joel.granados/linux.git/log/?h=jag/constify_proc_handlers