From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> Date: Wed, 24 Dec 2008 14:03:57 -0800 Subject: [PATCH 4/6][v5] Protect cinit from unblocked SIG_DFL signals Drop early any SIG_DFL or SIG_IGN signals to container-init from within the same container. But queue SIGSTOP and SIGKILL to the container-init if they are from an ancestor container. Blocked, fatal signals (i.e when SIG_DFL is to terminate) from within the container can still terminate the container-init. That will be addressed in the next patch. Note: To be bisect-safe, SIGNAL_UNKILLABLE will be set for container-inits in a follow-on patch. Until then, this patch is just a preparatory step. Changelog[v4]: - (Oleg Nesterov) Remove SIGNAL_UNKILLABLE_FROM_NS and rename 'same_ns' to 'from_ancestor_ns'. - SIGNAL_UNKILLABLE is not yet set for container-inits (will be set in follow-on patch). Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> --- kernel/signal.c | 36 +++++++++++++++++++++++++++--------- 1 files changed, 27 insertions(+), 9 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index f33100d..b51781e 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -53,20 +53,34 @@ static int sig_handler_ignored(void __user *handler, int sig) (handler == SIG_DFL && sig_kernel_ignore(sig)); } -static int sig_task_ignored(struct task_struct *t, int sig) +/* + * Return 1 if task @t is either the global init or the container-init + * of the sender's container. Return 0 otherwise. + */ +static int sig_task_unkillable(struct task_struct *t, int from_ancestor_ns) +{ + int flags = t->signal->flags; + + if (unlikely(flags & SIGNAL_UNKILLABLE) && !from_ancestor_ns) + return 1; + + return 0; +} + +static int sig_task_ignored(struct task_struct *t, int sig, int from_ancestor_ns) { void __user *handler; handler = sig_handler(t, sig); - if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && + if (sig_task_unkillable(t, from_ancestor_ns) && handler == SIG_DFL) return 1; - + return sig_handler_ignored(handler, sig); } -static int sig_ignored(struct task_struct *t, int sig) +static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns) { /* * Blocked signals are never ignored, since the @@ -76,7 +90,7 @@ static int sig_ignored(struct task_struct *t, int sig) if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig)) return 0; - if (!sig_task_ignored(t, sig)) + if (!sig_task_ignored(t, sig, from_ancestor_ns)) return 0; /* @@ -632,7 +646,7 @@ static int check_kill_permission(int sig, struct siginfo *info, * Returns true if the signal should be actually delivered, otherwise * it should be dropped. */ -static int prepare_signal(int sig, struct task_struct *p) +static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns) { struct signal_struct *signal = p->signal; struct task_struct *t; @@ -716,7 +730,7 @@ static int prepare_signal(int sig, struct task_struct *p) } } - return !sig_ignored(p, sig); + return !sig_ignored(p, sig, from_ancestor_ns); } /* @@ -881,11 +895,15 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t, { struct sigpending *pending; struct sigqueue *q; + int from_ancestor_ns; trace_sched_signal_send(sig, t); assert_spin_locked(&t->sighand->siglock); - if (!prepare_signal(sig, t)) + + from_ancestor_ns = siginfo_from_ancestor_ns(t, info); + + if (!prepare_signal(sig, t, from_ancestor_ns)) return 0; pending = group ? &t->signal->shared_pending : &t->pending; @@ -1380,7 +1398,7 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group) goto ret; ret = 1; /* the signal is ignored */ - if (!prepare_signal(sig, t)) + if (!prepare_signal(sig, t, 1)) goto out; ret = 0; -- 1.5.2.5 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers