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signals: protect cinit from unblocked SIG_DFL signals

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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>
This commit is contained in:
Sukadev Bhattiprolu 2009-04-02 16:58:05 -07:00 committed by Linus Torvalds
parent 7978b567d3
commit 921cf9f630
1 changed files with 19 additions and 9 deletions
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28
kernel/signal.c
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@ -55,20 +55,21 @@ static int sig_handler_ignored(void __user *handler, int sig)
(handler == SIG_DFL && sig_kernel_ignore(sig)); (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; void __user *handler;
handler = sig_handler(t, sig); handler = sig_handler(t, sig);
if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
handler == SIG_DFL) handler == SIG_DFL && !from_ancestor_ns)
return 1; return 1;
return sig_handler_ignored(handler, sig); 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 * Blocked signals are never ignored, since the
@ -78,7 +79,7 @@ static int sig_ignored(struct task_struct *t, int sig)
if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig)) if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
return 0; return 0;
if (!sig_task_ignored(t, sig)) if (!sig_task_ignored(t, sig, from_ancestor_ns))
return 0; return 0;
/* /*
@ -634,7 +635,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
* Returns true if the signal should be actually delivered, otherwise * Returns true if the signal should be actually delivered, otherwise
* it should be dropped. * 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 signal_struct *signal = p->signal;
struct task_struct *t; struct task_struct *t;
@ -718,7 +719,7 @@ static int prepare_signal(int sig, struct task_struct *p)
} }
} }
return !sig_ignored(p, sig); return !sig_ignored(p, sig, from_ancestor_ns);
} }
/* /*
@ -832,7 +833,8 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
trace_sched_signal_send(sig, t); trace_sched_signal_send(sig, t);
assert_spin_locked(&t->sighand->siglock); assert_spin_locked(&t->sighand->siglock);
if (!prepare_signal(sig, t))
if (!prepare_signal(sig, t, from_ancestor_ns))
return 0; return 0;
pending = group ? &t->signal->shared_pending : &t->pending; pending = group ? &t->signal->shared_pending : &t->pending;
@ -902,7 +904,15 @@ out_set:
static int send_signal(int sig, struct siginfo *info, struct task_struct *t, static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group) 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; int print_fatal_signals;
@ -1336,7 +1346,7 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
goto ret; goto ret;
ret = 1; /* the signal is ignored */ ret = 1; /* the signal is ignored */
if (!prepare_signal(sig, t)) if (!prepare_signal(sig, t, 0))
goto out; goto out;
ret = 0; ret = 0;