linux-stable.git/kernel/cgroup, branch linux-4.19.y

cgroup: Fix potential overflow issue when checking max_depth

2024-11-08T15:19:22+00:00

[ Upstream commit 3cc4e13bb1617f6a13e5e6882465984148743cf4 ]

cgroup.max.depth is the maximum allowed descent depth below the current
cgroup. If the actual descent depth is equal or larger, an attempt to
create a new child cgroup will fail. However due to the cgroup->max_depth
is of int type and having the default value INT_MAX, the condition
'level > cgroup->max_depth' will never be satisfied, and it will cause
an overflow of the level after it reaches to INT_MAX.

Fix it by starting the level from 0 and using '>=' instead.

It's worth mentioning that this issue is unlikely to occur in reality,
as it's impossible to have a depth of INT_MAX hierarchy, but should be
be avoided logically.

Fixes: 1a926e0bbab8 ("cgroup: implement hierarchy limits")
Signed-off-by: Xiu Jianfeng 
Reviewed-by: Michal Koutný 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup: Protect css->cgroup write under css_set_lock

2024-09-12T09:02:53+00:00

[ Upstream commit 57b56d16800e8961278ecff0dc755d46c4575092 ]

The writing of css->cgroup associated with the cgroup root in
rebind_subsystems() is currently protected only by cgroup_mutex.
However, the reading of css->cgroup in both proc_cpuset_show() and
proc_cgroup_show() is protected just by css_set_lock. That makes the
readers susceptible to racing problems like data tearing or caching.
It is also a problem that can be reported by KCSAN.

This can be fixed by using READ_ONCE() and WRITE_ONCE() to access
css->cgroup. Alternatively, the writing of css->cgroup can be moved
under css_set_lock as well which is done by this patch.

Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup/cpuset: Prevent UAF in proc_cpuset_show()

2024-09-04T11:13:07+00:00

commit 1be59c97c83ccd67a519d8a49486b3a8a73ca28a upstream.

An UAF can happen when /proc/cpuset is read as reported in [1].

This can be reproduced by the following methods:
1.add an mdelay(1000) before acquiring the cgroup_lock In the
 cgroup_path_ns function.
2.$cat /proc//cpuset   repeatly.
3.$mount -t cgroup -o cpuset cpuset /sys/fs/cgroup/cpuset/
$umount /sys/fs/cgroup/cpuset/   repeatly.

The race that cause this bug can be shown as below:

(umount)		|	(cat /proc//cpuset)
css_release		|	proc_cpuset_show
css_release_work_fn	|	css = task_get_css(tsk, cpuset_cgrp_id);
css_free_rwork_fn	|	cgroup_path_ns(css->cgroup, ...);
cgroup_destroy_root	|	mutex_lock(&cgroup_mutex);
rebind_subsystems	|
cgroup_free_root 	|
			|	// cgrp was freed, UAF
			|	cgroup_path_ns_locked(cgrp,..);

When the cpuset is initialized, the root node top_cpuset.css.cgrp
will point to &cgrp_dfl_root.cgrp. In cgroup v1, the mount operation will
allocate cgroup_root, and top_cpuset.css.cgrp will point to the allocated
&cgroup_root.cgrp. When the umount operation is executed,
top_cpuset.css.cgrp will be rebound to &cgrp_dfl_root.cgrp.

The problem is that when rebinding to cgrp_dfl_root, there are cases
where the cgroup_root allocated by setting up the root for cgroup v1
is cached. This could lead to a Use-After-Free (UAF) if it is
subsequently freed. The descendant cgroups of cgroup v1 can only be
freed after the css is released. However, the css of the root will never
be released, yet the cgroup_root should be freed when it is unmounted.
This means that obtaining a reference to the css of the root does
not guarantee that css.cgrp->root will not be freed.

Fix this problem by using rcu_read_lock in proc_cpuset_show().
As cgroup_root is kfree_rcu after commit d23b5c577715
("cgroup: Make operations on the cgroup root_list RCU safe"),
css->cgroup won't be freed during the critical section.
To call cgroup_path_ns_locked, css_set_lock is needed, so it is safe to
replace task_get_css with task_css.

[1] https://syzkaller.appspot.com/bug?extid=9b1ff7be974a403aa4cd

Fixes: a79a908fd2b0 ("cgroup: introduce cgroup namespaces")
Signed-off-by: Chen Ridong 
Signed-off-by: Tejun Heo 
Signed-off-by: Shivani Agarwal 
Signed-off-by: Greg Kroah-Hartman

sched/fair: Allow disabling sched_balance_newidle with sched_relax_domain_level

2024-06-16T11:23:32+00:00

[ Upstream commit a1fd0b9d751f840df23ef0e75b691fc00cfd4743 ]

Change relax_domain_level checks so that it would be possible
to include or exclude all domains from newidle balancing.

This matches the behavior described in the documentation:

  -1   no request. use system default or follow request of others.
   0   no search.
   1   search siblings (hyperthreads in a core).

"2" enables levels 0 and 1, level_max excludes the last (level_max)
level, and level_max+1 includes all levels.

Fixes: 1d3504fcf560 ("sched, cpuset: customize sched domains, core")
Signed-off-by: Vitalii Bursov 
Signed-off-by: Ingo Molnar 
Tested-by: Dietmar Eggemann 
Reviewed-by: Vincent Guittot 
Reviewed-by: Valentin Schneider 
Link: https://lore.kernel.org/r/bd6de28e80073c79466ec6401cdeae78f0d4423d.1714488502.git.vitaly@bursov.com
Signed-off-by: Sasha Levin

cgroup: Remove duplicates in cgroup v1 tasks file

2023-10-25T09:16:34+00:00

commit 1ca0b605150501b7dc59f3016271da4eb3e96fce upstream.

One PID may appear multiple times in a preloaded pidlist.
(Possibly due to PID recycling but we have reports of the same
task_struct appearing with different PIDs, thus possibly involving
transfer of PID via de_thread().)

Because v1 seq_file iterator uses PIDs as position, it leads to
a message:
> seq_file: buggy .next function kernfs_seq_next did not update position index

Conservative and quick fix consists of removing duplicates from `tasks`
file (as opposed to removing pidlists altogether). It doesn't affect
correctness (it's sufficient to show a PID once), performance impact
would be hidden by unconditional sorting of the pidlist already in place
(asymptotically).

Link: https://lore.kernel.org/r/20230823174804.23632-1-mkoutny@suse.com/
Suggested-by: Firo Yang 
Signed-off-by: Michal Koutný 
Signed-off-by: Tejun Heo 
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

cgroup:namespace: Remove unused cgroup_namespaces_init()

2023-09-23T08:48:08+00:00

[ Upstream commit 82b90b6c5b38e457c7081d50dff11ecbafc1e61a ]

cgroup_namspace_init() just return 0. Therefore, there is no need to
call it during start_kernel. Just remove it.

Fixes: a79a908fd2b0 ("cgroup: introduce cgroup namespaces")
Signed-off-by: Lu Jialin 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup: Do not corrupt task iteration when rebinding subsystem

2023-06-28T08:15:28+00:00

commit 6f363f5aa845561f7ea496d8b1175e3204470486 upstream.

We found a refcount UAF bug as follows:

refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 342 at lib/refcount.c:25 refcount_warn_saturate+0xa0/0x148
Workqueue: events cpuset_hotplug_workfn
Call trace:
 refcount_warn_saturate+0xa0/0x148
 __refcount_add.constprop.0+0x5c/0x80
 css_task_iter_advance_css_set+0xd8/0x210
 css_task_iter_advance+0xa8/0x120
 css_task_iter_next+0x94/0x158
 update_tasks_root_domain+0x58/0x98
 rebuild_root_domains+0xa0/0x1b0
 rebuild_sched_domains_locked+0x144/0x188
 cpuset_hotplug_workfn+0x138/0x5a0
 process_one_work+0x1e8/0x448
 worker_thread+0x228/0x3e0
 kthread+0xe0/0xf0
 ret_from_fork+0x10/0x20

then a kernel panic will be triggered as below:

Unable to handle kernel paging request at virtual address 00000000c0000010
Call trace:
 cgroup_apply_control_disable+0xa4/0x16c
 rebind_subsystems+0x224/0x590
 cgroup_destroy_root+0x64/0x2e0
 css_free_rwork_fn+0x198/0x2a0
 process_one_work+0x1d4/0x4bc
 worker_thread+0x158/0x410
 kthread+0x108/0x13c
 ret_from_fork+0x10/0x18

The race that cause this bug can be shown as below:

(hotplug cpu)                | (umount cpuset)
mutex_lock(&cpuset_mutex)    | mutex_lock(&cgroup_mutex)
cpuset_hotplug_workfn        |
 rebuild_root_domains        |  rebind_subsystems
  update_tasks_root_domain   |   spin_lock_irq(&css_set_lock)
   css_task_iter_start       |    list_move_tail(&cset->e_cset_node[ss->id]
   while(css_task_iter_next) |                  &dcgrp->e_csets[ss->id]);
   css_task_iter_end         |   spin_unlock_irq(&css_set_lock)
mutex_unlock(&cpuset_mutex)  | mutex_unlock(&cgroup_mutex)

Inside css_task_iter_start/next/end, css_set_lock is hold and then
released, so when iterating task(left side), the css_set may be moved to
another list(right side), then it->cset_head points to the old list head
and it->cset_pos->next points to the head node of new list, which can't
be used as struct css_set.

To fix this issue, switch from all css_sets to only scgrp's css_sets to
patch in-flight iterators to preserve correct iteration, and then
update it->cset_head as well.

Reported-by: Gaosheng Cui 
Link: https://www.spinics.net/lists/cgroups/msg37935.html
Suggested-by: Michal Koutný 
Link: https://lore.kernel.org/all/20230526114139.70274-1-xiujianfeng@huaweicloud.com/
Signed-off-by: Xiu Jianfeng 
Fixes: 2d8f243a5e6e ("cgroup: implement cgroup->e_csets[]")
Cc: stable@vger.kernel.org # v3.16+
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

cgroup/cpuset: Wake up cpuset_attach_wq tasks in cpuset_cancel_attach()

2023-04-20T10:04:40+00:00

commit ba9182a89626d5f83c2ee4594f55cb9c1e60f0e2 upstream.

After a successful cpuset_can_attach() call which increments the
attach_in_progress flag, either cpuset_cancel_attach() or cpuset_attach()
will be called later. In cpuset_attach(), tasks in cpuset_attach_wq,
if present, will be woken up at the end. That is not the case in
cpuset_cancel_attach(). So missed wakeup is possible if the attach
operation is somehow cancelled. Fix that by doing the wakeup in
cpuset_cancel_attach() as well.

Fixes: e44193d39e8d ("cpuset: let hotplug propagation work wait for task attaching")
Signed-off-by: Waiman Long 
Reviewed-by: Michal Koutný 
Cc: stable@vger.kernel.org # v3.11+
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

cgroup: Add missing cpus_read_lock() to cgroup_attach_task_all()

2023-04-05T09:15:43+00:00

commit 43626dade36fa74d3329046f4ae2d7fdefe401c6 upstream.

syzbot is hitting percpu_rwsem_assert_held(&cpu_hotplug_lock) warning at
cpuset_attach() [1], for commit 4f7e7236435ca0ab ("cgroup: Fix
threadgroup_rwsem <-> cpus_read_lock() deadlock") missed that
cpuset_attach() is also called from cgroup_attach_task_all().
Add cpus_read_lock() like what cgroup_procs_write_start() does.

Link: https://syzkaller.appspot.com/bug?extid=29d3a3b4d86c8136ad9e [1]
Reported-by: syzbot 
Signed-off-by: Tetsuo Handa 
Fixes: 4f7e7236435ca0ab ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock")
Signed-off-by: Tejun Heo 
Signed-off-by: Cai Xinchen 
Signed-off-by: Greg Kroah-Hartman

cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock

2023-04-05T09:15:43+00:00

commit 4f7e7236435ca0abe005c674ebd6892c6e83aeb3 upstream.

Add #include  to avoid compile error on some architectures.

commit 9a3284fad42f6 ("cgroup: Optimize single thread migration") and
commit 671c11f0619e5 ("cgroup: Elide write-locking threadgroup_rwsem
when updating csses on an empty subtree") are not backport. So ignore the
input parameter of cgroup_attach_lock/cgroup_attach_unlock.

original commit message:

Bringing up a CPU may involve creating and destroying tasks which requires
read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
cpus_read_lock(). However, cpuset's ->attach(), which may be called with
thredagroup_rwsem write-locked, also wants to disable CPU hotplug and
acquires cpus_read_lock(), leading to a deadlock.

Fix it by guaranteeing that ->attach() is always called with CPU hotplug
disabled and removing cpus_read_lock() call from cpuset_attach().

Signed-off-by: Tejun Heo 
Reviewed-and-tested-by: Imran Khan 
Reported-and-tested-by: Xuewen Yan 
Fixes: 05c7b7a92cc8 ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug")
Cc: stable@vger.kernel.org # v5.17+
Signed-off-by: Cai Xinchen 
Signed-off-by: Greg Kroah-Hartman