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>
[mkoutny: Adjust for pre-fs_context, duplicate mount/remount check, drop log messages.]
Acked-by: Michal Koutný <mkoutny@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup/cgroup-v1.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -577,6 +577,14 @@ 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;
@@ -1048,6 +1056,7 @@ static int cgroup1_remount(struct kernfs
{
int ret = 0;
struct cgroup_root *root = cgroup_root_from_kf(kf_root);
+ struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct cgroup_sb_opts opts;
u16 added_mask, removed_mask;
@@ -1061,6 +1070,12 @@ static int cgroup1_remount(struct kernfs
if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
task_tgid_nr(current), current->comm);
+ /* See cgroup1_mount release_agent handling */
+ if (opts.release_agent &&
+ ((ns->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
added_mask = opts.subsys_mask & ~root->subsys_mask;
removed_mask = root->subsys_mask & ~opts.subsys_mask;
@@ -1224,6 +1239,15 @@ struct dentry *cgroup1_mount(struct file
ret = -EPERM;
goto out_unlock;
}
+ /*
+ * Release agent gets called with all capabilities,
+ * require capabilities to set release agent.
+ */
+ if (opts.release_agent &&
+ ((ns->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root) {
