linux-kernel - [PATCH 2/4] signals: send_signal: use si_fromuser() to detect from_ancestor

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Message-ID: <20091004021954.GC21006@redhat.com>
Date:	Sun, 4 Oct 2009 04:19:54 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Daniel Lezcano <dlezcano@...ibm.com>,
	Sukadev Bhattiprolu <sukadev@...ibm.com>,
	Linux Containers <containers@...ts.osdl.org>,
	roland@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] signals: send_signal: use si_fromuser() to detect
	from_ancestor_ns

Change send_signal() to use si_fromuser(). From now SEND_SIG_NOINFO
triggers the "from_ancestor_ns" check.

This fixes reparent_thread()->group_send_sig_info(pdeath_signal)
behaviour, before this patch send_signal() does not detect the
cross-namespace case when the child of the dying parent belongs
to the sub-namespace.

This patch can affect the behaviour of send_sig(), kill_pgrp() and
kill_pid() when the caller sends the signal to the sub-namespace
with "priv == 0" but surprisingly all callers seem to use them
correctly, including disassociate_ctty(on_exit).

Except: drivers/staging/comedi/drivers/addi-data/*.c incorrectly
use send_sig(priv => 0). But his is minor and should be fixed
anyway.

Reported-by: Daniel Lezcano <dlezcano@...ibm.com>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---

 kernel/signal.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- TTT_32/kernel/signal.c~FU_2_SEND_SIGNAL	2009-10-04 02:21:55.000000000 +0200
+++ TTT_32/kernel/signal.c	2009-10-04 03:09:44.000000000 +0200
@@ -928,9 +928,8 @@ static int send_signal(int sig, struct s
 	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;
+	from_ancestor_ns = si_fromuser(info) &&
+			   !task_pid_nr_ns(current, task_active_pid_ns(t));
 #endif

 	return __send_signal(sig, info, t, group, from_ancestor_ns);

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