It was found that some hotplug operations may cause multiple rebuild_sched_domains_locked() calls. Some of those intermediate calls may use cpuset states not in the final correct form leading to incorrect sched domain setting. Fix this problem by using the existing force_rebuild flag to inhibit immediate rebuild_sched_domains_locked() calls if set and only doing one final call at the end. Also renaming the force_rebuild flag to force_sd_rebuild to make its meaning for clear. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Commit e2ffe502ba45 ("cgroup/cpuset: Add cpuset.cpus.exclusive for
v2") adds a user writable cpuset.cpus.exclusive file for setting
exclusive CPUs to be used for the creation of partitions. Since then
effective_xcpus depends on both the cpuset.cpus and cpuset.cpus.exclusive
setting. If cpuset.cpus.exclusive is set, effective_xcpus will depend
only on cpuset.cpus.exclusive. When it is not set, effective_xcpus
will be set according to the cpuset.cpus value when the cpuset becomes
a valid partition root.
When cpuset.cpus is being cleared by the user, effective_xcpus should
only be cleared when cpuset.cpus.exclusive is not set. However, that
is not currently the case.
# cd /sys/fs/cgroup/
# mkdir test
# echo +cpuset > cgroup.subtree_control
# cd test
# echo 3 > cpuset.cpus.exclusive
# cat cpuset.cpus.exclusive.effective
3
# echo > cpuset.cpus
# cat cpuset.cpus.exclusive.effective // was cleared
Fix it by clearing effective_xcpus only if cpuset.cpus.exclusive is
not set.
Fixes: e2ffe502ba45 ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
Cc: stable@vger.kernel.org # v6.7+
Reported-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
We find a bug as below:
BUG: unable to handle page fault for address: 00000003
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 358 Comm: bash Tainted: G W I 6.6.0-10893-g60d6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/4
RIP: 0010:partition_sched_domains_locked+0x483/0x600
Code: 01 48 85 d2 74 0d 48 83 05 29 3f f8 03 01 f3 48 0f bc c2 89 c0 48 9
RSP: 0018:ffffc90000fdbc58 EFLAGS: 00000202
RAX: 0000000100000003 RBX: ffff888100b3dfa0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000002fe80
RBP: ffff888100b3dfb0 R08: 0000000000000001 R09: 0000000000000000
R10: ffffc90000fdbcb0 R11: 0000000000000004 R12: 0000000000000002
R13: ffff888100a92b48 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f44a5425740(0000) GS:ffff888237d80000(0000) knlGS:0000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100030973 CR3: 000000010722c000 CR4: 00000000000006e0
Call Trace:
<TASK>
? show_regs+0x8c/0xa0
? __die_body+0x23/0xa0
? __die+0x3a/0x50
? page_fault_oops+0x1d2/0x5c0
? partition_sched_domains_locked+0x483/0x600
? search_module_extables+0x2a/0xb0
? search_exception_tables+0x67/0x90
? kernelmode_fixup_or_oops+0x144/0x1b0
? __bad_area_nosemaphore+0x211/0x360
? up_read+0x3b/0x50
? bad_area_nosemaphore+0x1a/0x30
? exc_page_fault+0x890/0xd90
? __lock_acquire.constprop.0+0x24f/0x8d0
? __lock_acquire.constprop.0+0x24f/0x8d0
? asm_exc_page_fault+0x26/0x30
? partition_sched_domains_locked+0x483/0x600
? partition_sched_domains_locked+0xf0/0x600
rebuild_sched_domains_locked+0x806/0xdc0
update_partition_sd_lb+0x118/0x130
cpuset_write_resmask+0xffc/0x1420
cgroup_file_write+0xb2/0x290
kernfs_fop_write_iter+0x194/0x290
new_sync_write+0xeb/0x160
vfs_write+0x16f/0x1d0
ksys_write+0x81/0x180
__x64_sys_write+0x21/0x30
x64_sys_call+0x2f25/0x4630
do_syscall_64+0x44/0xb0
entry_SYSCALL_64_after_hwframe+0x78/0xe2
RIP: 0033:0x7f44a553c887
It can be reproduced with cammands:
cd /sys/fs/cgroup/
mkdir test
cd test/
echo +cpuset > ../cgroup.subtree_control
echo root > cpuset.cpus.partition
cat /sys/fs/cgroup/cpuset.cpus.effective
0-3
echo 0-3 > cpuset.cpus // taking away all cpus from root
This issue is caused by the incorrect rebuilding of scheduling domains.
In this scenario, test/cpuset.cpus.partition should be an invalid root
and should not trigger the rebuilding of scheduling domains. When calling
update_parent_effective_cpumask with partcmd_update, if newmask is not
null, it should recheck newmask whether there are cpus is available
for parect/cs that has tasks.
Fixes: 0c7f293efc87 ("cgroup/cpuset: Add cpuset.cpus.exclusive.effective for v2")
Cc: stable@vger.kernel.org # v6.7+
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently the event counting provided by misc.events is hierarchical, it's not practical if user is only concerned with events of a specified cgroup. Therefore, introduce misc.events.local collect events specific to the given cgroup. This is analogous to memory.events.local and pids.events.local. Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
In the function cgroup_base_stat_cputime_show, there are five instances of #ifdef, which makes the code not concise. To address this, add the function cgroup_force_idle_show to make the code more succinct. Signed-off-by: Chen Ridong <chenridong@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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 <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Introduce misc.peak to record the historical maximum usage of the resource, as in some scenarios the value of misc.max could be adjusted based on the peak usage of the resource. Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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.$cat /proc/<pid>/cpuset repeatly.
3.$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/<pid>/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 <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The "cpuset.cpus.exclusive.effective" value is currently limited to a subset of its "cpuset.cpus". This makes the exclusive CPUs distribution hierarchy subsumed within the larger "cpuset.cpus" hierarchy. We have to decide on what CPUs are used locally and what CPUs can be passed down as exclusive CPUs down the hierarchy and combine them into "cpuset.cpus". The advantage of the current scheme is to have only one hierarchy to worry about. However, it make it harder to use as all the "cpuset.cpus" values have to be properly set along the way down to the designated remote partition root. It also makes it more cumbersome to find out what CPUs can be used locally. Make creation of remote partition simpler by breaking the dependency of "cpuset.cpus.exclusive" on "cpuset.cpus" and make them independent entities. Now we have two separate hierarchies - one for setting "cpuset.cpus.effective" and the other one for setting "cpuset.cpus.exclusive.effective". We may not need to set "cpuset.cpus" when we activate a partition root anymore. Also update Documentation/admin-guide/cgroup-v2.rst and cpuset.c comment to document this change. Suggested-by: Petr Malat <oss@malat.biz> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>