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Commit 0e8283cb 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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2fd752ed

kernel/cgroup/cgroup-v1.c

+14 −0
Original line number Diff line number Diff line
@@ -549,6 +549,14 @@ 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;
@@ -961,6 +969,12 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param) 
		/* 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;