diff mbox series

[SRU,Bionic,1/1] cgroup-v1: Require capabilities to set release_agent

Message ID 20220214133514.233255-2-cascardo@canonical.com
State New
Headers show
Series CVE-2022-0492 | expand

Commit Message

Thadeu Lima de Souza Cascardo Feb. 14, 2022, 1:35 p.m. UTC 
From: "Eric W. Biederman" <ebiederm@xmission.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@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>
[mkoutny: Adjust for pre-fs_context, duplicate mount/remount check, drop log messages.]
Acked-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit b391bb3554dd6e04b7a8ede975dbd3342526a045 linux-4.14.y)
CVE-2022-0492
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
---
 kernel/cgroup/cgroup-v1.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
diff mbox series

Patch

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 5602bd81caa9..105f5b2f5978 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -577,6 +577,14 @@  static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
 
 	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;
@@ -1060,6 +1068,7 @@  static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
 {
 	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;
 
@@ -1073,6 +1082,12 @@  static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
 	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;
@@ -1236,6 +1251,15 @@  struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 		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) {