linux-kernel - Re: [PATCH 2/6] parport: Remove register_sysctl_table from parport_proc

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Date:   Tue, 16 May 2023 18:12:21 +0200
From:   Joel Granados <j.granados@...sung.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
CC:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 2/6] parport: Remove register_sysctl_table from
 parport_proc_register

On Tue, May 16, 2023 at 04:31:16PM +0200, Joel Granados wrote:
> On Mon, May 15, 2023 at 09:17:39PM -0700, Luis Chamberlain wrote:
> > Awesome!
> > 
> > On Mon, May 15, 2023 at 09:14:42AM +0200, Joel Granados wrote:
> > > +
> > > +	port_name_len = strnlen(port->name, PARPORT_NAME_MAX_LEN);
> > > +	/*
> > > +	 * Allocate a buffer for two paths: dev/parport/PORT and dev/parport/PORT/devices.
> > > +	 * We calculate for the second as that will give us enough for the first.
> > > +	 */
> > > +	tmp_path_len = PARPORT_BASE_DEVICES_PATH_SIZE + port_name_len;
> > > +	tmp_dir_path = kmalloc(tmp_path_len, GFP_KERNEL);
> > 
> > Any reason why not kzalloc()?
> nope. Will zero it out.
> 
> > 
> > > +	if (!tmp_dir_path) {
> > > +		err = -ENOMEM;
> > > +		goto exit_free_t;
> > > +	}
> > >  
> > > -	t->port_dir[0].procname = port->name;
> > > +	if (tmp_path_len
> > > +	    <= snprintf(tmp_dir_path, tmp_path_len, "dev/parport/%s/devices", port->name)) {
> > 
> > Since we are clearing up obfuscation code, it would be nicer to
> > make this easier to read and split the snprintf() into one line, capture
> > the error there. And then in a new line do the check. Even if we have to
> > add a new int value here.
> np. Will do something like this:
> 
> num_chars_sprinted = snprintf(....
> if(tmp_path_len <= num_chars_sprinted) {
>   err = -ENOENT;
>   ...
> }
> 
> > 
> > Other than this I'd just ask to extend the commit log to use
> > the before and after of vmlinux (when this module is compiled in with all
> > the bells and whistles) with ./scripts/bloat-o-meter.
> > 
> > Ie build before the patch and cp vmlinux to vmlinux.old and then compare
> > with:
> > 
> > ./scripts/bloat-o-meter vmlinux.old vmlinux
> > 
> > Can you also describe any testing if any.
> Sure thing. Will add the bloat-o-meter output on the last patch so as to
> gather the results for all the patches.
> 
> I'll write some testing info on the patches.
> 
> 
> > 
> > With the above changes, feel free to add to all these patches:
> > 
> > Reviewed-by: Luis Chamberlain
> Ack
> 
> > 
> > > +	if (register_sysctl(tmp_dir_path, t->device_dir) == NULL)
> > 
> > BTW, we should be able to remove now replace register_sysctl_base() with a simple
> > register_sysctl("kernel", foo), and then one for "fs", and one of "vm"
> > on kernel/sysctl.c and just remove:
> > 
> >   * DECLARE_SYSCTL_BASE() & register_sysctl_base() & __register_sysctl_base()
> >   * and then after all this register_sysctl_table() completely
> > 
> > Let me know if you'd like a stab at it, or if you prefer me to do that.
> I think I can give it a go. Should I just add that to these set of
> patches? or should we create a new patch set?
I'll send the V2 of this patch set without this. Will add it to the
patch set when I finish if it makes sense. Else I'll just create a new
series.

Best

-- 

Joel Granados

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