signals: 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.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index 7b6de96..fb19aae 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -55,20 +55,21 @@
(handler == SIG_DFL && sig_kernel_ignore(sig));
}
-static int sig_task_ignored(struct task_struct *t, int sig)
+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) &&
- handler == SIG_DFL)
+ handler == SIG_DFL && !from_ancestor_ns)
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
@@ -78,7 +79,7 @@
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;
/*
@@ -634,7 +635,7 @@
* 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;
@@ -718,7 +719,7 @@
}
}
- return !sig_ignored(p, sig);
+ return !sig_ignored(p, sig, from_ancestor_ns);
}
/*
@@ -832,7 +833,8 @@
trace_sched_signal_send(sig, t);
assert_spin_locked(&t->sighand->siglock);
- if (!prepare_signal(sig, t))
+
+ if (!prepare_signal(sig, t, from_ancestor_ns))
return 0;
pending = group ? &t->signal->shared_pending : &t->pending;
@@ -902,7 +904,15 @@
static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group)
{
- return __send_signal(sig, info, t, group, 0);
+ int from_ancestor_ns = 0;
+
+#ifdef CONFIG_PID_NS
+ if (!is_si_special(info) && SI_FROMUSER(info) &&
+ task_pid_nr_ns(current, task_active_pid_ns(t)) <= 0)
+ from_ancestor_ns = 1;
+#endif
+
+ return __send_signal(sig, info, t, group, from_ancestor_ns);
}
int print_fatal_signals;
@@ -1336,7 +1346,7 @@
goto ret;
ret = 1; /* the signal is ignored */
- if (!prepare_signal(sig, t))
+ if (!prepare_signal(sig, t, 0))
goto out;
ret = 0;