linux-kernel - Re: [PATCH][next] clone3: fix an unsigned args.cgroup comparison to less than zero

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Date:   Mon, 24 Feb 2020 13:25:03 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Colin King <colin.king@...onical.com>,
        Christian Brauner <christian@...uner.io>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH][next] clone3: fix an unsigned args.cgroup comparison to
 less than zero

On Mon, Feb 24, 2020 at 10:31:57AM +0300, Dan Carpenter wrote:
> On Sat, Feb 22, 2020 at 01:18:01PM +0100, Christian Brauner wrote:
> > On Sat, Feb 22, 2020 at 12:15:13AM +0000, Colin King wrote:
> > > From: Colin Ian King <colin.king@...onical.com>
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 2diff --git a/kernel/fork.c b/kernel/fork.c
> > index 2853e258fe1f..dca4dde3b5b2 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -2618,7 +2618,8 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
> >                      !valid_signal(args.exit_signal)))
> >                 return -EINVAL;
> > 
> > -       if ((args.flags & CLONE_INTO_CGROUP) && args.cgroup < 0)
> > +       if ((args.flags & CLONE_INTO_CGROUP) &&
> > +           (args.cgroup > INT_MAX || (s64)args.cgroup < 0))
> 
> If we're capping it at INT_MAX then the check for negative isn't
> required and static analysis tools know it's not so they might complain.

It isn't, but it's easier to understand for the reader. But I don't care
that much and if it's trouble for tools than fine.

Christian