cgroup-v1: Require capabilities to set release_agent
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.
BUG=b/213421437
TEST=presubmit
RELEASE_NOTE=This resolves CVE-2022-0492
cos-patch: security-moderate
Reported-by: Tabitha Sable <tabitha.c.sable@gmail.com>
Tested-by: Tabitha Sable <tabitha.c.sable@gmail.com>
Fixes: 81a6a5cdd2c5 ("Task Control Groups: automatic userspace notification of idle cgroups")
Cc: stable@vger.kernel.org # v2.6.24+
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: Ic0f4f84376ec2adcfc390672211a19bc59b8a280
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/29041
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Tested-by: Roy Yang <royyang@google.com>
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 2d0ef61..5e465c4 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -549,6 +549,14 @@
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;
@@ -961,6 +969,12 @@
/* Specifying two release agents is forbidden */
if (ctx->release_agent)
return cg_invalf(fc, "cgroup1: 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 cg_invalf(fc, "cgroup1: Setting release_agent not allowed");
ctx->release_agent = param->string;
param->string = NULL;
break;
