From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sukadev Bhattiprolu Subject: [RFC][PATCH 5/6][v3] Protect cinit from unblocked SIG_DFL signals Date: Sat, 20 Dec 2008 16:54:54 -0800 Message-ID: <20081221005454.GE5025@us.ibm.com> References: <20081221005106.GA4912@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20081221005106.GA4912@us.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: oleg@redhat.com, ebiederm@xmission.com, roland@redhat.com, bastian@waldi.eu.org Cc: daniel@hozac.com, xemul@openvz.org, containers@lists.osdl.org, linux-kernel@vger.kernel.org, sukadev@us.ibm.com List-Id: containers.vger.kernel.org From: Sukadev Bhattiprolu Date: Sat, 20 Dec 2008 13:25:24 -0800 Subject: [RFC][PATCH 5/6][v3] 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 acnestor 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. Signed-off-by: Sukadev Bhattiprolu --- kernel/signal.c | 43 ++++++++++++++++++++++++++++++++++--------- 1 files changed, 34 insertions(+), 9 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 058b4c0..2dfca62 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -53,20 +53,39 @@ 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. + * + * @same_ns = 1 indicates that sender of signal is in same pid namespace + * as sender. + */ +static int sig_task_unkillable(struct task_struct *t, int same_ns) +{ + int flags = t->signal->flags; + + if (unlikely(flags & SIGNAL_UNKILLABLE) || + (same_ns && (flags & SIGNAL_UNKILLABLE_FROM_NS))) + return 1; + + return 0; +} + +static int sig_task_ignored(struct task_struct *t, int sig, int same_ns) { void __user *handler; handler = sig_handler(t, sig); - if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && + if (sig_task_unkillable(t, same_ns) && (handler == SIG_IGN || 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 same_ns) { /* * Blocked signals are never ignored, since the @@ -76,7 +95,7 @@ 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, same_ns)) return 0; /* @@ -632,7 +651,7 @@ 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 same_ns) { struct signal_struct *signal = p->signal; struct task_struct *t; @@ -716,7 +735,7 @@ static int prepare_signal(int sig, struct task_struct *p) } } - return !sig_ignored(p, sig); + return !sig_ignored(p, sig, same_ns); } /* @@ -867,11 +886,17 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t, { struct sigpending *pending; struct sigqueue *q; + int same_ns; trace_sched_signal_send(sig, t); assert_spin_locked(&t->sighand->siglock); - if (!prepare_signal(sig, t)) + + same_ns = 1; + if (siginfo_from_ancestor_ns(t, info)) + same_ns = 0; + + if (!prepare_signal(sig, t, same_ns)) return 0; pending = group ? &t->signal->shared_pending : &t->pending; @@ -1366,7 +1391,7 @@ 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