Gitweb: http://git.kernel.org/linus/f008faff0e2777c8b3fe853891b774ca465938d8
Commit: f008faff0e2777c8b3fe853891b774ca465938d8
Parent: 43918f2bf4806675943416d539d9d5e4d585ebff
Author: Oleg Nesterov <oleg@redhat.com>
AuthorDate: Thu Apr 2 16:58:02 2009 -0700
Committer: Linus Torvalds <torvalds@linux-foundation.org>
CommitDate: Thu Apr 2 19:04:58 2009 -0700
signals: 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.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
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>
---
kernel/signal.c | 16 +++++++++++++---
1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index 92a1ab0..8bf7a40 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -55,10 +55,21 @@ 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
@@ -67,8 +78,7 @@ 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;
/*
--
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