From nobody Mon Feb 9 23:58:04 2026 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 779EC26FDA7 for ; Fri, 9 May 2025 07:06:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746774419; cv=none; b=STalB10nXpEK+Pp8/9s/QeN6tuXK+DltAgFvbUFivYZp5wNdBAGmqZVke5xqqjo8HHLISSn1jecWlHth8i2b6Wc4lSaHBDQetitBrMi/c1JAasysx0cf8kZkWZGSfNUNPHcXIDav/3ZN18Y4DmlHRXF1AaMHxNWmgUjZnsMEnPU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746774419; c=relaxed/simple; bh=xuh3+d3PyJHPLx/vRAjNd3dPRlG+l4xvonJuqToDVxA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=dnQn4OK+HPaloRkrt32NZA4izGwncqa/qprBk5RD8bhNUaxklcBk3fKcRPxRlq5+V60fq2ECCFrgYVBNhUtqFRYp1cJiyNdI3l9WjvOXtodCQfQaJpiZ6DOp1IMe+5YO3uX/DMlMj+LhSSI8zfnw0kB0GObHZTUw/zFk862JDDQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4Zv0R959F8z4f3jch for ; Fri, 9 May 2025 15:06:29 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.252]) by mail.maildlp.com (Postfix) with ESMTP id 4ED5B1A0847 for ; Fri, 9 May 2025 15:06:54 +0800 (CST) Received: from hulk-vt.huawei.com (unknown [10.67.174.121]) by APP3 (Coremail) with SMTP id _Ch0CgAnesR4qR1ofcXLLg--.60961S11; Fri, 09 May 2025 15:06:54 +0800 (CST) From: Chen Ridong To: akpm@linux-foundation.org, paulmck@kernel.org, bigeasy@linutronix.de, legion@kernel.org, roman.gushchin@linux.dev, brauner@kernel.org, tglx@linutronix.de, frederic@kernel.org, peterz@infradead.org, oleg@redhat.com, joel.granados@kernel.org, viro@zeniv.linux.org.uk, lorenzo.stoakes@oracle.com, avagin@google.com, mengensun@tencent.com, linux@weissschuh.net, jlayton@kernel.org, ruanjinjie@huawei.com, kees@kernel.org Cc: linux-kernel@vger.kernel.org, lujialin4@huawei.com, chenridong@huaweicloud.com Subject: [RFC next 3/5] user_namespace: add user_ns iteration helper Date: Fri, 9 May 2025 06:54:15 +0000 Message-Id: <20250509065417.147515-10-chenridong@huaweicloud.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250509065417.147515-1-chenridong@huaweicloud.com> References: <20250509065417.147515-1-chenridong@huaweicloud.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 X-CM-TRANSID: _Ch0CgAnesR4qR1ofcXLLg--.60961S11 X-Coremail-Antispam: 1UD129KBjvJXoWxGF43KFWfZF1Utry7Gw4fGrg_yoW5XFWDpF 4Skr9xAw47JrnrKwn8ZFs5u34fWr10vFy8JFyxu3s3tF1agFy5Arn7A3WrZr9xGr4UGrW5 XFWUKws8Kr4Uu37anT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUmS14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWrXVW3AwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_GFv_WrylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF 4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBI daVFxhVjvjDU0xZFpf9x0pRUDGrUUUUU= X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ Content-Type: text/plain; charset="utf-8" From: Chen Ridong Add a helper function named 'ns_next_child_pre' that performs a pre-order traversal of a namespace's descendants. Signed-off-by: Chen Ridong --- include/linux/user_namespace.h | 9 +++++++ kernel/user_namespace.c | 44 ++++++++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+) diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index d84b2703caab..823df9267a4a 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -169,6 +169,15 @@ static inline void set_userns_rlimit_max(struct user_n= amespace *ns, ns->rlimit_max[type] =3D max <=3D LONG_MAX ? max : LONG_MAX; } =20 +struct user_namespace *ns_next_child(struct user_namespace *pos, + struct user_namespace *parent); +struct user_namespace *ns_next_child_pre(struct user_namespace *pos, + struct user_namespace *root); + +#define ns_for_each_child_pre(pos, ns) \ + for ((pos) =3D ns_next_child_pre(NULL, (ns)); (pos); \ + (pos) =3D ns_next_child_pre((pos), (ns))) + #ifdef CONFIG_USER_NS =20 static inline struct user_namespace *get_user_ns(struct user_namespace *ns) diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index cbe8f96c3e60..9a2e77505b97 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -30,6 +30,50 @@ static bool new_idmap_permitted(const struct file *file, struct uid_gid_map *map); static void free_user_ns(struct work_struct *work); =20 +struct user_namespace *ns_next_child(struct user_namespace *pos, + struct user_namespace *parent) +{ + struct user_namespace *next; + + if (!pos) + /* Get the first child of the parent. */ + next =3D list_entry_rcu(parent->children.next, struct user_namespace, ns= _node); + else + next =3D list_entry_rcu(pos->ns_node.next, struct user_namespace, ns_nod= e); + + if (&next->ns_node !=3D &parent->children) + return next; + + return NULL; +} + +/* Should be called under rcu_read_lock() */ +struct user_namespace *ns_next_child_pre(struct user_namespace *pos, + struct user_namespace *root) +{ + struct user_namespace *next; + + + /* if first iteration, visit @root */ + if (!pos) + return root; + + /* visit the first child if exists */ + next =3D ns_next_child(NULL, pos); + if (next) + return next; + + /* no child, visit my or the closest ancestor's next ns_node */ + while (pos !=3D root) { + next =3D ns_next_child(pos, pos->parent); + if (next) + return next; + pos =3D pos->parent; + } + + return NULL; +} + static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid= _t uid) { return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES); --=20 2.34.1