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Mon, 21 Jul 2025 18:40:53 -0700 (PDT) From: JP Kobryn To: tj@kernel.org, shakeel.butt@linux.dev, mkoutny@suse.com, yosryahmed@google.com, hannes@cmpxchg.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, kernel-team@meta.com Subject: [PATCH 4/5 cgroup/for-6.16-fixes] cgroup: initialize css rstat before linking to cgroups in css_create() Date: Mon, 21 Jul 2025 18:40:29 -0700 Message-ID: <20250722014030.297537-5-inwardvessel@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250722014030.297537-1-inwardvessel@gmail.com> References: <20250722014030.297537-1-inwardvessel@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Calling css_rstat_init() after linking the css with its cgroup (and parent cgroup) leaves the code vulnerable to async cleanup where css_rstat_exit() is invoked on a fully initialized css. Avoid this by calling css_rstat_init() before linking. The error can then be handled inline with no async cleanup requirement. Signed-off-by: JP Kobryn --- kernel/cgroup/cgroup.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 1990c6113c7f..0f8c6ce21634 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5675,6 +5675,15 @@ static struct cgroup_subsys_state *css_create(struct= cgroup *cgrp, return css; =20 init_css(css); + + if (ss->css_rstat_flush) { + err =3D css_rstat_init(css); + if (err) { + ss->css_free(css); + goto err_out; + } + } + link_css(css, ss, cgrp); =20 err =3D percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL); @@ -5686,12 +5695,6 @@ static struct cgroup_subsys_state *css_create(struct= cgroup *cgrp, goto err_free_css; css->id =3D err; =20 - if (ss->css_rstat_flush) { - err =3D css_rstat_init(css); - if (err) - goto err_free_css; - } - /* @css is ready to be brought online now, make it visible */ list_add_tail_rcu(&css->sibling, &parent_css->children); cgroup_idr_replace(&ss->css_idr, css, css->id); @@ -5707,6 +5710,7 @@ static struct cgroup_subsys_state *css_create(struct = cgroup *cgrp, err_free_css: INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); +err_out: return ERR_PTR(err); } =20 --=20 2.47.1