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cgroup: Add generic cgroup subsystem permission checks.

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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>
This commit is contained in:
San Mehat 2009-05-21 14:10:06 -07:00 committed by Colin Cross
parent 22e9cd9dc9
commit 1d38bc7d05
4 changed files with 34 additions and 0 deletions
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10
kernel/cgroup.c
View File

@ -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 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
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);

8
kernel/cgroup_freezer.c
View File

@ -164,6 +164,14 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
{
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.
*/

7
kernel/cpuset.c
View File

@ -1373,6 +1373,13 @@ static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
{
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;

9
kernel/sched.c
View File

@ -8803,6 +8803,15 @@ cpu_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
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;