From patchwork Wed Apr 29 00:16:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 1278784 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: incoming-bpf@patchwork.ozlabs.org Delivered-To: patchwork-incoming-bpf@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=bpf-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=fb.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=fb.com header.i=@fb.com header.a=rsa-sha256 header.s=facebook header.b=aIgwU73z; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49BfFb6fSzz9sSX for ; Wed, 29 Apr 2020 10:16:35 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726503AbgD2AQe (ORCPT ); Tue, 28 Apr 2020 20:16:34 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:18052 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726363AbgD2AQd (ORCPT ); Tue, 28 Apr 2020 20:16:33 -0400 Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 03T0EuEm000377 for ; Tue, 28 Apr 2020 17:16:32 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=ye6YhMYI9YmUaRCK4h4wCdCahyZXWawHKAl8V7kGQ6M=; b=aIgwU73z70SV5XQ0PvaTGI5WgAvpWji7pfCH4+Co7PVfvt710cQqvSs2wTXWZr69Gs0s /em9no2TGz/65NtFFhTEOUVLw5I0bNHwyTjzML2q+avOMGPVuyOxJCZKIIRIavmMIzxO MIfBq4/LvLIxKCfHttNTjv/jS1JuKIvG4W8= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 30nq53wvye-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 28 Apr 2020 17:16:32 -0700 Received: from intmgw001.03.ash8.facebook.com (2620:10d:c085:108::8) by mail.thefacebook.com (2620:10d:c085:11d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1847.3; Tue, 28 Apr 2020 17:16:30 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id B2C5F2EC309B; Tue, 28 Apr 2020 17:16:24 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Andrii Nakryiko Smtp-Origin-Hostname: devbig012.ftw2.facebook.com To: , , , CC: , , Andrii Nakryiko Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v3 bpf-next 03/10] bpf: support GET_FD_BY_ID and GET_NEXT_ID for bpf_link Date: Tue, 28 Apr 2020 17:16:07 -0700 Message-ID: <20200429001614.1544-4-andriin@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200429001614.1544-1-andriin@fb.com> References: <20200429001614.1544-1-andriin@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-28_15:2020-04-28,2020-04-28 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=999 spamscore=0 lowpriorityscore=0 suspectscore=8 impostorscore=0 priorityscore=1501 phishscore=0 bulkscore=0 malwarescore=0 adultscore=0 mlxscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004290000 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Add support to look up bpf_link by ID and iterate over all existing bpf_links in the system. GET_FD_BY_ID code handles not-yet-ready bpf_link by checking that its ID hasn't been set to non-zero value yet. Setting bpf_link's ID is done as the very last step in finalizing bpf_link, together with installing FD. This approach allows users of bpf_link in kernel code to not worry about races between user-space and kernel code that hasn't finished attaching and initializing bpf_link. Signed-off-by: Andrii Nakryiko --- include/uapi/linux/bpf.h | 2 ++ kernel/bpf/syscall.c | 49 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 51 insertions(+) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 6121aa487465..7e6541fceade 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -113,6 +113,8 @@ enum bpf_cmd { BPF_MAP_DELETE_BATCH, BPF_LINK_CREATE, BPF_LINK_UPDATE, + BPF_LINK_GET_FD_BY_ID, + BPF_LINK_GET_NEXT_ID, }; enum bpf_map_type { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 5439e05e3d25..1c213a730502 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3713,6 +3713,48 @@ static int link_update(union bpf_attr *attr) return ret; } +static int bpf_link_inc_not_zero(struct bpf_link *link) +{ + return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? 0 : -ENOENT; +} + +#define BPF_LINK_GET_FD_BY_ID_LAST_FIELD link_id + +static int bpf_link_get_fd_by_id(const union bpf_attr *attr) +{ + struct bpf_link *link; + u32 id = attr->link_id; + int fd, err; + + if (CHECK_ATTR(BPF_LINK_GET_FD_BY_ID)) + return -EINVAL; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + spin_lock_bh(&link_idr_lock); + link = idr_find(&link_idr, id); + /* before link is "settled", ID is 0, pretend it doesn't exist yet */ + if (link) { + if (link->id) + err = bpf_link_inc_not_zero(link); + else + err = -EAGAIN; + } else { + err = -ENOENT; + } + spin_unlock_bh(&link_idr_lock); + + if (err) + return err; + + fd = bpf_link_new_fd(link); + if (fd < 0) + bpf_link_put(link); + + return fd; +} + SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size) { union bpf_attr attr; @@ -3830,6 +3872,13 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz case BPF_LINK_UPDATE: err = link_update(&attr); break; + case BPF_LINK_GET_FD_BY_ID: + err = bpf_link_get_fd_by_id(&attr); + break; + case BPF_LINK_GET_NEXT_ID: + err = bpf_obj_get_next_id(&attr, uattr, + &link_idr, &link_idr_lock); + break; default: err = -EINVAL; break;