>From 491e532e336a98b1b9d1ecda6f4160d0c0adde89 Mon Sep 17 00:00:00 2001
From: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: Thu, 29 Nov 2007 08:18:16 -0800
Subject: [PATCH 3/4] user namespaces: enforce CAP_NS_OVERRIDE for
cross-namespace kill
Require CAP_NS_OVERRIDE to 'kill' across user namespaces.
If the signaling task is exiting, then current->nsproxy is
NULL. Since we are only notifying a parent of our death,
we permit the signal.
If the target task is exiting, our signal doesn't matter
anyway.
Signed-off-by: Serge Hallyn <[EMAIL PROTECTED]>
---
kernel/signal.c | 23 +++++++++++++++++++++++
1 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index 280bccb..de19433 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -531,9 +531,32 @@ static int check_kill_permission(int sig, struct siginfo
*info,
return error;
if (info == SEND_SIG_NOINFO || (!is_si_special(info) &&
SI_FROMUSER(info))) {
+ struct nsproxy *nsproxy;
+ struct user_namespace *my_user_ns = NULL, *t_user_ns = NULL;
+
error = audit_signal_info(sig, t); /* Let audit system see the
signal */
if (error)
return error;
+
+ /*
+ * if current->nsproxy is NULL, then we are exiting and
+ * are just sending an exit signal to our parent.
+ * Uid may be wrong under certain circumstances, but
+ * global init shouldn't care, and a container creation
+ * program should know what it is doing.
+ * If target is exiting then it doesn't matter anyway.
+ */
+ rcu_read_lock();
+ nsproxy = task_nsproxy(t);
+ if (nsproxy)
+ t_user_ns = nsproxy->user_ns;
+ rcu_read_unlock();
+ if (current->nsproxy)
+ my_user_ns = current->nsproxy->user_ns;
+ if (my_user_ns && t_user_ns && my_user_ns != t_user_ns
+ && !(capable(CAP_KILL) && capable(CAP_NS_OVERRIDE)))
+ return -EPERM;
+
error = -EPERM;
if (((sig != SIGCONT) ||
(task_session_nr(current) != task_session_nr(t)))
--
1.5.1
-
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