Re: [PATCH -mm v2] do_notify_parent: sanitize the valid_signal() checks

[Deepanshu Kartikey <kartikey406@gmail.com>]

On Tue, Mar 17, 2026 at 7:28 PM Oleg Nesterov <oleg@redhat.com> wrote:
>
> Now that kernel_clone() checks valid_signal(args->exit_signal), the "sig"
> argument of do_notify_parent() must always be valid or we have a bug.
>
> However, do_notify_parent() only checks that sig != -1 at the start, then
> it does another valid_signal() check before __send_signal_locked().
>
> This is confusing. Change do_notify_parent() to WARN and return early if
> valid_signal(sig) is false.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
>  kernel/signal.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 86aad7badb9a..683ef92f7234 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2171,7 +2171,8 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
>         bool autoreap = false;
>         u64 utime, stime;
>
> -       WARN_ON_ONCE(sig == -1);
> +       if (WARN_ON_ONCE(!valid_signal(sig)))
> +               return false;
>
>         /* do_notify_parent_cldstop should have been called instead.  */
>         WARN_ON_ONCE(task_is_stopped_or_traced(tsk));
> @@ -2252,7 +2253,7 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
>          * Send with __send_signal as si_pid and si_uid are in the
>          * parent's namespaces.
>          */
> -       if (valid_signal(sig) && sig)
> +       if (sig)
>                 __send_signal_locked(sig, &info, tsk->parent, PIDTYPE_TGID, false);
>         __wake_up_parent(tsk, tsk->parent);
>         spin_unlock_irqrestore(&psig->siglock, flags);
> --
> 2.52.0
>
>


Acked-by: Deepanshu Kartikey <Kartikey406@gmail.com>