From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
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@xxxxxxxxx>
Tested-by: Tabitha Sable <tabitha.c.sable@xxxxxxxxx>
Fixes: 81a6a5cdd2c5 ("Task Control Groups: automatic userspace notification of idle cgroups")
Cc: stable@xxxxxxxxxxxxxxx # v2.6.24+
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
