Re: [PATCH v4 4/6] treewide: use get_random_u32() when possible

Jason A. Donenfeld
2022-10-09T00:26:00Z

On Sat, Oct 8, 2022 at 4:37 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> On Sat, Oct 08, 2022 at 10:18:45PM +0000, David Laight wrote:
> > From: Jason A. Donenfeld
> > > Sent: 07 October 2022 19:01
> > >
> > > The prandom_u32() function has been a deprecated inline wrapper around
> > > get_random_u32() for several releases now, and compiles down to the
> > > exact same code. Replace the deprecated wrapper with a direct call to
> > > the real function. The same also applies to get_random_int(), which is
> > > just a wrapper around get_random_u32().
> > >
> > ...
> > > diff --git a/net/802/garp.c b/net/802/garp.c
> > > index f6012f8e59f0..c1bb67e25430 100644
> > > --- a/net/802/garp.c
> > > +++ b/net/802/garp.c
> > > @@ -407,7 +407,7 @@ static void garp_join_timer_arm(struct garp_applicant *app)
> > > {
> > > unsigned long delay;
> > >
> > > - delay = (u64)msecs_to_jiffies(garp_join_time) * prandom_u32() >> 32;
> > > + delay = (u64)msecs_to_jiffies(garp_join_time) * get_random_u32() >> 32;
> > > mod_timer(&app->join_timer, jiffies + delay);
> > > }
> > >
> > > diff --git a/net/802/mrp.c b/net/802/mrp.c
> > > index 35e04cc5390c..3e9fe9f5d9bf 100644
> > > --- a/net/802/mrp.c
> > > +++ b/net/802/mrp.c
> > > @@ -592,7 +592,7 @@ static void mrp_join_timer_arm(struct mrp_applicant *app)
> > > {
> > > unsigned long delay;
> > >
> > > - delay = (u64)msecs_to_jiffies(mrp_join_time) * prandom_u32() >> 32;
> > > + delay = (u64)msecs_to_jiffies(mrp_join_time) * get_random_u32() >> 32;
> > > mod_timer(&app->join_timer, jiffies + delay);
> > > }
> > >
> >
> > Aren't those:
> > delay = prandom_u32_max(msecs_to_jiffies(xxx_join_time));
>
> Probably, but too involved and peculiar for this cleanup.
>
> Feel free to send a particular patch to that maintainer.

I guess the cocci patch looks like this, so maybe I'll put that in 1/7
if I respin this.

@@
expression E;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u64;
@@
- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)