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Message-Id: <20220204091914.718640241@linuxfoundation.org>
Date: Fri, 4 Feb 2022 10:20:20 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Tabitha Sable <tabitha.c.sable@...il.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 5.10 13/25] cgroup-v1: Require capabilities to set release_agent
From: Eric W. Biederman <ebiederm@...ssion.com>
commit 24f6008564183aa120d07c03d9289519c2fe02af upstream.
The cgroup release_agent is called with call_usermodehelper. The function
call_usermodehelper starts the release_agent with a full set fo capabilities.
Therefore require capabilities when setting the release_agaent.
Reported-by: Tabitha Sable <tabitha.c.sable@...il.com>
Tested-by: Tabitha Sable <tabitha.c.sable@...il.com>
Fixes: 81a6a5cdd2c5 ("Task Control Groups: automatic userspace notification of idle cgroups")
Cc: stable@...r.kernel.org # v2.6.24+
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
kernel/cgroup/cgroup-v1.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -545,6 +545,14 @@ static ssize_t cgroup_release_agent_writ
BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
+ /*
+ * Release agent gets called with all capabilities,
+ * require capabilities to set release agent.
+ */
+ if ((of->file->f_cred->user_ns != &init_user_ns) ||
+ !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
cgrp = cgroup_kn_lock_live(of->kn, false);
if (!cgrp)
return -ENODEV;
@@ -958,6 +966,12 @@ int cgroup1_parse_param(struct fs_contex
/* Specifying two release agents is forbidden */
if (ctx->release_agent)
return invalfc(fc, "release_agent respecified");
+ /*
+ * Release agent gets called with all capabilities,
+ * require capabilities to set release agent.
+ */
+ if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))
+ return invalfc(fc, "Setting release_agent not allowed");
ctx->release_agent = param->string;
param->string = NULL;
break;
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