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From:   Richard Guy Briggs <rgb@redhat.com>
To:     cgroups@vger.kernel.org, containers@lists.linux-foundation.org,
        linux-api@vger.kernel.org,
        Linux-Audit Mailing List <linux-audit@redhat.com>,
        linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        netdev@vger.kernel.org
Cc:     luto@kernel.org, jlayton@redhat.com, carlos@redhat.com,
        viro@zeniv.linux.org.uk, dhowells@redhat.com, simo@redhat.com,
        eparis@parisplace.org, serge@hallyn.com, ebiederm@xmission.com,
        madzcar@gmail.com, Richard Guy Briggs <rgb@redhat.com>
Subject: [RFC PATCH ghak32 V2 02/13] audit: check children and threading before allowing containerid
Date:   Fri, 16 Mar 2018 05:00:29 -0400
Message-Id: <995b77557010b2f9aed0e10435f7b8536df7a5db.1521179281.git.rgb@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Check if a task has existing children or co-threads and refuse to set
the container ID if either are present.  Failure to check this could
permit games where a child scratches its parent's back to work around
inheritance and double-setting policy.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
 kernel/auditsc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 29c8482..a6b0a52 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2087,6 +2087,10 @@ static int audit_set_containerid_perm(struct task_struct *task, u64 containerid)
 	/* if we don't have caps, reject */
 	if (!capable(CAP_AUDIT_CONTROL))
 		return -EPERM;
+	/* if task has children or is not single-threaded, deny */
+	if (!list_empty(&task->children) ||
+	    !(thread_group_leader(task) && thread_group_empty(task)))
+		return -EPERM;
 	/* if containerid is unset, allow */
 	if (!audit_containerid_set(task))
 		return 0;
-- 
1.8.3.1