From: Quanyang Wang <quanyang.wang@windriver.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Roman Gushchin <guro@fb.com>,
mkoutny@suse.com, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [V2][PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline
Date: Tue, 19 Oct 2021 18:41:58 +0800 [thread overview]
Message-ID: <bf88f85b-59a4-e2de-8b3a-70871e63adf6@windriver.com> (raw)
In-Reply-To: <YW1vuXh4C4tX9ZHP@T590>
Hi Ming,
On 10/18/21 8:59 PM, Ming Lei wrote:
> On Mon, Oct 18, 2021 at 06:06:28PM +0800, Quanyang Wang wrote:
>> Hi Ming,
>>
>> On 10/18/21 5:02 PM, Ming Lei wrote:
>>> On Mon, Oct 18, 2021 at 03:56:23PM +0800, quanyang.wang@windriver.com wrote:
>>>> From: Quanyang Wang <quanyang.wang@windriver.com>
>>>>
>>>> When enabling CONFIG_CGROUP_BPF, kmemleak can be observed by running
>>>> the command as below:
>>>>
>>>> $mount -t cgroup -o none,name=foo cgroup cgroup/
>>>> $umount cgroup/
>>>>
>>>> unreferenced object 0xc3585c40 (size 64):
>>>> comm "mount", pid 425, jiffies 4294959825 (age 31.990s)
>>>> hex dump (first 32 bytes):
>>>> 01 00 00 80 84 8c 28 c0 00 00 00 00 00 00 00 00 ......(.........
>>>> 00 00 00 00 00 00 00 00 6c 43 a0 c3 00 00 00 00 ........lC......
>>>> backtrace:
>>>> [<e95a2f9e>] cgroup_bpf_inherit+0x44/0x24c
>>>> [<1f03679c>] cgroup_setup_root+0x174/0x37c
>>>> [<ed4b0ac5>] cgroup1_get_tree+0x2c0/0x4a0
>>>> [<f85b12fd>] vfs_get_tree+0x24/0x108
>>>> [<f55aec5c>] path_mount+0x384/0x988
>>>> [<e2d5e9cd>] do_mount+0x64/0x9c
>>>> [<208c9cfe>] sys_mount+0xfc/0x1f4
>>>> [<06dd06e0>] ret_fast_syscall+0x0/0x48
>>>> [<a8308cb3>] 0xbeb4daa8
>>>>
>>>> This is because that since the commit 2b0d3d3e4fcf ("percpu_ref: reduce
>>>> memory footprint of percpu_ref in fast path") root_cgrp->bpf.refcnt.data
>>>> is allocated by the function percpu_ref_init in cgroup_bpf_inherit which
>>>> is called by cgroup_setup_root when mounting, but not freed along with
>>>> root_cgrp when umounting. Adding cgroup_bpf_offline which calls
>>>> percpu_ref_kill to cgroup_kill_sb can free root_cgrp->bpf.refcnt.data in
>>>> umount path.
>>>>
>>>> This patch also fixes the commit 4bfc0bb2c60e ("bpf: decouple the lifetime
>>>> of cgroup_bpf from cgroup itself"). A cgroup_bpf_offline is needed to do a
>>>> cleanup that frees the resources which are allocated by cgroup_bpf_inherit
>>>> in cgroup_setup_root.
>>>>
>>>> And inside cgroup_bpf_offline, cgroup_get() is at the beginning and
>>>> cgroup_put is at the end of cgroup_bpf_release which is called by
>>>> cgroup_bpf_offline. So cgroup_bpf_offline can keep the balance of
>>>> cgroup's refcount.
>>>>
>>>> Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
>>>
>>> If I understand correctly, cgroup_bpf_release() won't be called without
>>> your patch. So anything allocated in cgroup_bpf_inherit() will be
>>> leaked?
>> No, for now cgroup_bpf_release is called to release bpf.refcnt.data of the
>> cgroup which is not root_cgroup. Only root_cgroup's bpf data is leaked.
>
> You mean that cgroup_bpf_inherit() allocates nothing for root_cgroup?
>
> If yes, I agree you can add 'Fixes: 2b0d3d3e4fcf', otherwise please
> remove it.
>
>
> Thanks,
> Ming
>
next prev parent reply other threads:[~2021-10-19 10:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 7:56 [V2][PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline quanyang.wang
2021-10-18 9:02 ` Ming Lei
2021-10-18 10:06 ` Quanyang Wang
2021-10-18 12:59 ` Ming Lei
2021-10-19 10:41 ` Quanyang Wang
2021-10-19 17:10 ` Michal Koutný
2021-10-20 2:17 ` Ming Lei
2021-10-20 5:22 ` Quanyang Wang
2021-10-20 17:28 ` Michal Koutný
2021-10-22 11:03 ` Quanyang Wang
2021-10-20 5:16 ` Quanyang Wang
2021-10-19 10:41 ` Quanyang Wang [this message]
2021-10-22 1:30 ` Roman Gushchin
2021-10-22 11:55 ` Quanyang Wang
2021-10-22 21:29 ` Alexei Starovoitov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bf88f85b-59a4-e2de-8b3a-70871e63adf6@windriver.com \
--to=quanyang.wang@windriver.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=axboe@kernel.dk \
--cc=bpf@vger.kernel.org \
--cc=cgroups@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=guro@fb.com \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizefan.x@bytedance.com \
--cc=ming.lei@redhat.com \
--cc=mkoutny@suse.com \
--cc=netdev@vger.kernel.org \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).