linux-kernel - Re: [PATCH v5] sysctl: simplify the min/max boundary check

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Message-ID: <csfegppvkhnl33x37335dsxdxmlzn7jairgsucxl5rdo3d6yzi@2z3nfgtcy7eg>
Date: Mon, 10 Mar 2025 15:25:16 +0100
From: Joel Granados <joel.granados@...nel.org>
To: Wen Yang <wen.yang@...ux.dev>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, 
	Luis Chamberlain <mcgrof@...nel.org>, Kees Cook <keescook@...omium.org>, 
	Christian Brauner <brauner@...nel.org>, Dave Young <dyoung@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] sysctl: simplify the min/max boundary check

On Thu, Mar 06, 2025 at 09:33:39PM +0800, Wen Yang wrote:
> 
> 
> On 2025/3/3 17:26, Joel Granados wrote:
> > On Thu, Jan 30, 2025 at 10:32:14PM +0800, Wen Yang wrote:
> > > 
> > > 
> > > On 2025/1/28 01:51, Eric W. Biederman wrote:
> > > > Joel Granados <joel.granados@...nel.org> writes:
> > > > 
> > > > > On Thu, Jan 23, 2025 at 12:30:25PM -0600, Eric W. Biederman wrote:
> > > > > > "Eric W. Biederman" <ebiederm@...ssion.com> writes:
> > > > > > 
> > > > > > > Joel Granados <joel.granados@...nel.org> writes:
> > > > > > > 
> > > > > > > > On Sun, Jan 19, 2025 at 10:59:21PM +0800, Wen Yang wrote:
> > ...
...
> > Quick question: Do you have a systemic way of identifying these? Do you
> > have a grep or awk scripts somewhere? I'm actually very interested in
> > finding out what is the impact of this.
> > 
> 
> Thanks, we may use the following simple scripts:
> 
> - the extra {1,2} as pointers to some objects:
> $ grep "\.extra1\|\.extra2" * -R | grep -v "SYSCTL_" | grep -v "\&"
This is actually pretty nice. Thx for that. I executed it a bit
differently: 

$  git grep "\.extra1\|\.extra2" | grep -v "SYSCTL_" | grep -v "&"

I also went and did something way more complicated :). I created an
smatch check [1] and ran it on a allyes config. This gave me all of your
results except the openat2 selftests. This might be something to
consider for when this is finished to add a check so that ppl don't just
add an int or a long to a extra

Best

[1]: https://github.com/Joelgranados/smatch/tree/jag/extra_ptr



> 
> - the extra {1,2} as pointers to elements in the shared constant array:
> $ grep "\.extra1\|\.extra2" * -R | grep "SYSCTL_"
> 
> - the extra {1,2} as pointers to additional constant variables:
> $ grep "\.extra1\|\.extra2" * -R | grep "\&"
> 
> 
> --
> Best wishes,
> Wen
> 
> 
> > 
> > 
> > > 
> > > 
> > > So could we modify it in this way to make it compatible with these two
> > > situations:
> > > 
> > > @@ -137,8 +137,16 @@ struct ctl_table {
> > >          umode_t mode;
> > >          proc_handler *proc_handler;     /* Callback for text formatting */
> > >          struct ctl_table_poll *poll;
> > > -       void *extra1;
> > > -       void *extra2;
> > > +       union {
> > > +               struct {
> > > +                       void *extra1;
> > > +                       void *extra2;
> > > +               };
> > > +               struct {
> > > +                       unsigned long min;
> > > +                       unsigned long max;
> > > +               };
> > > +       };
> > >   } __randomize_layout;
> > > 
> > > 
> > > --
> > > Best wishes,
> > > Wen
> > > 
> > 

-- 

Joel Granados