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Commit 939f8b49 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Greg Kroah-Hartman
Browse files

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.

Reported-by: default avatarTabitha Sable <tabitha.c.sable@gmail.com>
Tested-by: default avatarTabitha Sable <tabitha.c.sable@gmail.com>
Fixes: 81a6a5cd ("Task Control Groups: automatic userspace notification of idle cgroups")
Cc: stable@vger.kernel.org # v2.6.24+
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
[mkoutny: Adjust for pre-fs_context, duplicate mount/remount check, drop log messages.]
Acked-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 940b1065

kernel/cgroup/cgroup-v1.c

+24 −0
Original line number Diff line number Diff line
@@ -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;
@@ -1048,6 +1056,7 @@ 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;
@@ -1061,6 +1070,12 @@ 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;
@@ -1224,6 +1239,15 @@ 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) {