Re: [PATCH] seccomp: Add SECCOMP_CLONE_FILTER operation

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

On Wed, Sep 3, 2025 at 1:52 PM Tom Hromatka <tom.hromatka@xxxxxxxxxx> wrote:
>
> On 9/3/25 2:45 PM, Alexei Starovoitov wrote:
> > On Wed, Sep 3, 2025 at 1:38 PM Tom Hromatka <tom.hromatka@xxxxxxxxxx> wrote:
> >>
> >> +
> >> +       spin_lock_irq(&current->sighand->siglock);
> >> +       spin_lock_irq(&task->sighand->siglock);
> >> +
> >> +       if (atomic_read(&task->seccomp.filter_count) == 0) {
> >> +               spin_unlock_irq(&task->sighand->siglock);
> >> +               spin_unlock_irq(&current->sighand->siglock);
> >
> > did you copy this pattern from somewhere ?
> > It's obviously buggy.
>
> I tried to mimic the logic in copy_seccomp() in kernel/fork.c,
> but as you point out, I probably messed it up :).
>
> Do you have recommendations for a better design pattern?

Several things look wrong here.
Double _irq() is one obvious bug.
Grabbing spin_lock to do atomic_read() is another oddity.