linux-kernel - Re: [PATCH v2 13/18] sysctl: move sysctl type to ctl_table

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Date:   Thu, 7 Dec 2023 13:05:57 +0100
From:   Joel Granados <j.granados@...sung.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
CC:     Thomas Weißschuh <linux@...ssschuh.net>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-hardening@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2 13/18] sysctl: move sysctl type to ctl_table_header

On Tue, Dec 05, 2023 at 02:50:01PM -0800, Luis Chamberlain wrote:
> On Tue, Dec 5, 2023 at 2:41 PM Thomas Weißschuh <linux@...ssschuh.net> wrote:
> >
> > On 2023-12-05 14:33:38-0800, Luis Chamberlain wrote:
> > > On Mon, Dec 04, 2023 at 08:52:26AM +0100, Thomas Weißschuh wrote:
> > > > @@ -231,7 +231,8 @@ static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
> > > >             return -EROFS;
> > > >
> > > >     /* Am I creating a permanently empty directory? */
> > > > -   if (sysctl_is_perm_empty_ctl_header(header)) {
> > > > +   if (header->ctl_table == sysctl_mount_point ||
> > > > +       sysctl_is_perm_empty_ctl_header(header)) {
> > > >             if (!RB_EMPTY_ROOT(&dir->root))
> > > >                     return -EINVAL;
> > > >             sysctl_set_perm_empty_ctl_header(dir_h);
> > >
> > > While you're at it.
> >
> > This hunk is completely gone in v3/the code that you merged.
> 
> It is worse in that it is not obvious:
> 
> +       if (table == sysctl_mount_point)
> +               sysctl_set_perm_empty_ctl_header(head);
Notice that the test is done on the header and the set is done on the
dir_h.

I mention this because here you wrote:
"sysctl_set_perm_empty_ctl_header(head)"
instead of
"sysctl_set_perm_empty_ctl_header(dir_h)"

dir_h and head are different.

Was this your concern? or did I miss your point?
> 
> > Which kind of unsafety do you envision here?
> 
> Making the code obvious during patch review hy this is needed /
> special, and if we special case this, why not remove enum, and make it
> specific to only that one table. The catch is that it is not
> immediately obvious that we actually call
> sysctl_set_perm_empty_ctl_header() in other places, and it begs the
> question if this can be cleaned up somehow.
> 
>   Luis

-- 

Joel Granados

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