On Thu, Feb 10, 2022 at 3:53 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> Fatal SIGSYS signals were not being delivered to pid namespace init
> processes. Make sure the SIGNAL_UNKILLABLE doesn't get set for these
> cases.
>
> Reported-by: Robert Święcki <robert@xxxxxxxxxxx>
> Suggested-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> Fixes: 00b06da29cf9 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> kernel/signal.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 38602738866e..33e3ee4f3383 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1342,9 +1342,10 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t,
> }
> /*
> * Don't clear SIGNAL_UNKILLABLE for traced tasks, users won't expect
> - * debugging to leave init killable.
> + * debugging to leave init killable, unless it is intended to exit.
> */
> - if (action->sa.sa_handler == SIG_DFL && !t->ptrace)
> + if (action->sa.sa_handler == SIG_DFL &&
> + (!t->ptrace || (handler == HANDLER_EXIT)))
> t->signal->flags &= ~SIGNAL_UNKILLABLE;
You're changing the subclause:
!t->ptrace
to:
(!t->ptrace || (handler == HANDLER_EXIT))
which means that the change only affects cases where the process has a
ptracer, right? That's not the scenario the commit message is talking
about...
> ret = send_signal(sig, info, t, PIDTYPE_PID);
> spin_unlock_irqrestore(&t->sighand->siglock, flags);
> --
> 2.30.2
>
