From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> Date: Wed, 24 Dec 2008 14:04:24 -0800 Subject: [PATCH 5/6][v5] Protect cinit from blocked fatal signals Normally SIG_DFL signals to global and container-init are dropped early. But if a signal is blocked when it is posted, we cannot drop the signal since the receiver may install a handler before unblocking the signal. Once this signal is queued however, the receiver container-init has no way of knowing if the signal was sent from an ancestor or descendant namespace. This patch ensures that contianer-init drops all SIG_DFL signals in get_signal_to_deliver() except SIGKILL/SIGSTOP. If SIGSTOP/SIGKILL originate from a descendant of container-init they are never queued (i.e dropped in sig_ignored() in an earler patch). If SIGSTOP/SIGKILL originate from parent namespace, the signal is queued and container-init processes the signal. And now that we have all pieces in place, set SIGNAL_UNKILLABLE for container-inits. Changelog[v5]: - (Oleg Nesterov) Drop signal_unkillable(), simplify check in get_signal_to_deliver() and drop check for signal_group_exit() since it is covered by sig_kernel_only(). Changelog[v4]: - Rename sig_unkillable() to unkillable_by_sig() - Remove SIGNAL_UNKILLABLE_FROM_NS flag and simplify (Oleg Nesterov) - Set SIGNAL_UNKILLABLE for container-init in this patch. Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> --- kernel/fork.c | 2 ++ kernel/signal.c | 6 ++++-- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index dba2d3f..d3e93ef 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -812,6 +812,8 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) atomic_set(&sig->live, 1); init_waitqueue_head(&sig->wait_chldexit); sig->flags = 0; + if (clone_flags & CLONE_NEWPID) + sig->flags |= SIGNAL_UNKILLABLE; sig->group_exit_code = 0; sig->group_exit_task = NULL; sig->group_stop_count = 0; diff --git a/kernel/signal.c b/kernel/signal.c index b51781e..d90b033 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1914,9 +1914,11 @@ relock: /* * Global init gets no signals it doesn't want. + * Container-init gets no signals it doesn't want from same + * container. */ - if (unlikely(signal->flags & SIGNAL_UNKILLABLE) && - !signal_group_exit(signal)) + if ((signal->flags & SIGNAL_UNKILLABLE) && + !sig_kernel_only(signr)) continue; if (sig_kernel_stop(signr)) { -- 1.5.2.5 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers