Messages in this thread Patch in this message | | | Date | Tue, 6 Jan 2009 23:50:19 -0800 | From | Sukadev Bhattiprolu <> | Subject | [PATCH 2/7][v6] Protect init from unwanted signals more |
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From: Oleg Nesterov <oleg@redhat.com> Date: Wed, 24 Dec 2008 13:35:23 -0800 Subject: [PATCH 2/7][v6] Protect init from unwanted signals more
(This is a modified version of the patch submitted by Oleg Nesterov http://lkml.org/lkml/2008/11/18/249 and tries to address comments that came up in that discussion)
init ignores the SIG_DFL signals but we queue them anyway, including SIGKILL. This is mostly OK, the signal will be dropped silently when dequeued, but the pending SIGKILL has 2 bad implications:
- it implies fatal_signal_pending(), so we confuse things like wait_for_completion_killable/lock_page_killable.
- for the sub-namespace inits, the pending SIGKILL can mask (legacy_queue) the subsequent SIGKILL from the parent namespace which must kill cinit reliably. (preparation, cinits don't have SIGNAL_UNKILLABLE yet)
The patch can't help when init is ptraced, but ptracing of init is not "safe" anyway.
Changelog[v5]: - (Oleg Nesterov) Remove SIG_IGN check in sig_task_ignored() and let sig_handler_ignored() check SIG_IGN.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Acked-by: Roland McGrath <roland@redhat.com> --- kernel/signal.c | 16 +++++++++++++--- 1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c index 7945e71..87f3f30 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -53,10 +53,21 @@ static int sig_handler_ignored(void __user *handler, int sig) (handler == SIG_DFL && sig_kernel_ignore(sig)); } -static int sig_ignored(struct task_struct *t, int sig) +static int sig_task_ignored(struct task_struct *t, int sig) { void __user *handler; + handler = sig_handler(t, sig); + + if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && + handler == SIG_DFL) + return 1; + + return sig_handler_ignored(handler, sig); +} + +static int sig_ignored(struct task_struct *t, int sig) +{ /* * Blocked signals are never ignored, since the * signal handler may change by the time it is @@ -65,8 +76,7 @@ static int sig_ignored(struct task_struct *t, int sig) if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig)) return 0; - handler = sig_handler(t, sig); - if (!sig_handler_ignored(handler, sig)) + if (!sig_task_ignored(t, sig)) return 0; /* -- 1.5.2.5
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