commit 1d38bc7d0523af2233b4280e2aeab34c6a076665
author San Mehat <san@google.com> Thu May 21 14:10:06 2009 -0700
committer Colin Cross <ccross@android.com> Tue Jun 14 09:09:13 2011 -0700
tree 16c8c61cd13cc2e0d4fd879cc0cd87c893e867d6
parent 22e9cd9dc9b51f5ad96588ecbfde5f3221e0e6dd

cgroup: Add generic cgroup subsystem permission checks.

    Rather than using explicit euid == 0 checks when trying to move
tasks into a cgroup via CFS, move permission checks into each
specific cgroup subsystem. If a subsystem does not specify a
'can_attach' handler, then we fall back to doing our checks the old way.

    This way non-root processes can add arbitrary processes to
a cgroup if all the registered subsystems on that cgroup agree.

    Also change explicit euid == 0 check to CAP_SYS_ADMIN

Signed-off-by: San Mehat <san@google.com>

kernel/cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2731d11..129b47f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -58,6 +58,7 @@
 #include <linux/eventfd.h>
 #include <linux/poll.h>
 #include <linux/flex_array.h> /* used in cgroup_attach_proc */
+#include <linux/capability.h>
 
 #include <asm/atomic.h>
 
@@ -1839,6 +1840,15 @@
 				failed_ss = ss;
 				goto out;
 			}
+		} else if (!capable(CAP_SYS_ADMIN)) {
+			const struct cred *cred = current_cred(), *tcred;
+
+			/* No can_attach() - check perms generically */
+			tcred = __task_cred(tsk);
+			if (cred->euid != tcred->uid &&
+			    cred->euid != tcred->suid) {
+				return -EACCES;
+			}
 		}
 		if (ss->can_attach_task) {
 			retval = ss->can_attach_task(cgrp, tsk);

kernel/cgroup_freezer.c

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index e691818..6ebda1d 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -164,6 +164,14 @@
 {
 	struct freezer *freezer;
 
+	if ((current != task) && (!capable(CAP_SYS_ADMIN))) {
+		const struct cred *cred = current_cred(), *tcred;
+
+		tcred = __task_cred(task);
+		if (cred->euid != tcred->uid && cred->euid != tcred->suid)
+			return -EPERM;
+	}
+
 	/*
 	 * Anything frozen can't move or be moved to/from.
 	 */

kernel/cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 9c9b754..a1df487 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1373,6 +1373,13 @@
 {
 	struct cpuset *cs = cgroup_cs(cont);
 
+	if ((current != task) && (!capable(CAP_SYS_ADMIN))) {
+		const struct cred *cred = current_cred(), *tcred;
+
+		if (cred->euid != tcred->uid && cred->euid != tcred->suid)
+			return -EPERM;
+	}
+ 
 	if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
 		return -ENOSPC;
 

kernel/sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index ea7a385..13f13af 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8803,6 +8803,15 @@
 static int
 cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 {
+	if ((current != tsk) && (!capable(CAP_SYS_NICE))) {
+		const struct cred *cred = current_cred(), *tcred;
+
+		tcred = __task_cred(tsk);
+
+		if (cred->euid != tcred->uid && cred->euid != tcred->suid)
+			return -EPERM;
+	}
+
 #ifdef CONFIG_RT_GROUP_SCHED
 	if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
 		return -EINVAL;