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[2620:137:e000::1:20]) by mx.google.com with ESMTP id vl11-20020a17090730cb00b0088ac4402980si1113545ejb.489.2023.01.30.07.47.50; Mon, 30 Jan 2023 07:48:13 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=ib9tmd6T; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237025AbjA3PqI (ORCPT + 99 others); Mon, 30 Jan 2023 10:46:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237500AbjA3Ppp (ORCPT ); Mon, 30 Jan 2023 10:45:45 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3ACB3EFD8 for ; Mon, 30 Jan 2023 07:44:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675093495; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=XRAqDvpdOweYOp5rKoRnwrLbtMo4U87gO0dmZD+DZl8=; b=ib9tmd6T81o6xquV7W+ysOD93QZv+L4/I2AIvxF9A4ubGdOOTWldamW2tNpST8s+spMYem P/WaVQCAzUosHp2ZyzyWBgL92fg4P44MGApDTRWMUdA4t91ZkLBPlJ2EC5J+sFdApr1Ly+ T/027iLuDQUg8IYXB0vJUIiVG0hwMus= Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-88-vseZfI8tP_6BkmjycL97iQ-1; Mon, 30 Jan 2023 10:44:53 -0500 X-MC-Unique: vseZfI8tP_6BkmjycL97iQ-1 Received: by mail-pf1-f198.google.com with SMTP id h11-20020a056a00230b00b00593b9e6ee79so1633683pfh.8 for ; Mon, 30 Jan 2023 07:44:53 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=XRAqDvpdOweYOp5rKoRnwrLbtMo4U87gO0dmZD+DZl8=; b=XrSZYxQ0/loYxIOPP6nwbd1MfnoqBJzmVibfjxQvlUaU4H+NdC+/bcKxZIMimFZ5Bo xMwTHg5fcfYH0rc50/p1ZdLBYuHEvyXY63FGwUBo5zgSRXQCqIu1iDw8GdYiZq06odAh eW3gdwc5PVnn/qIHwqgw8sg6Q4j3X8xCN9vzyFpqRVh/B9RNzkCeKfk/FY7QFJcNIXgc wGGJw5UL2Gg11INj1bXrr9wF3FvhTEReE90IUUc9PznkWakJJfAjK/3XRWPyfvXQ/3zJ lgN6GXx9uRKIJGeoSeGyuo363TctKPRIBdHOVKm68i5AstmFngrNEXNAB2blRfIC1JgM RKHA== X-Gm-Message-State: AFqh2kpKUOMO43d5rTLFzIAoE/5Oye2tQUqH+5+VdUt8ERg6VkFvLoes vCA/EWyoTbGPy7HWcP6579wZJOAosLcpngv6DSmo8J5EfWu3evHzhoOii5x6hNsKyDyrFL+ppUz hr4oXtrdYF1GG8tQ7modMJkxl X-Received: by 2002:a17:90b:390b:b0:22b:b1cd:cce with SMTP id ob11-20020a17090b390b00b0022bb1cd0ccemr38598610pjb.33.1675093492643; Mon, 30 Jan 2023 07:44:52 -0800 (PST) X-Received: by 2002:a17:90b:390b:b0:22b:b1cd:cce with SMTP id ob11-20020a17090b390b00b0022bb1cd0ccemr38598587pjb.33.1675093492345; Mon, 30 Jan 2023 07:44:52 -0800 (PST) Received: from localhost.localdomain ([240d:1a:c0d:9f00:ca6:1aff:fead:cef4]) by smtp.gmail.com with ESMTPSA id mp1-20020a17090b190100b002298e0641b6sm9654421pjb.27.2023.01.30.07.44.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Jan 2023 07:44:52 -0800 (PST) From: Shigeru Yoshida To: jchapman@katalix.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Shigeru Yoshida Subject: [PATCH] l2tp: Avoid possible recursive deadlock in l2tp_tunnel_register() Date: Tue, 31 Jan 2023 00:44:38 +0900 Message-Id: <20230130154438.1373750-1-syoshida@redhat.com> X-Mailer: git-send-email 2.39.0 MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1756463045492734405?= X-GMAIL-MSGID: =?utf-8?q?1756463045492734405?= When a file descriptor of pppol2tp socket is passed as file descriptor of UDP socket, a recursive deadlock occurs in l2tp_tunnel_register(). This situation is reproduced by the following program: int main(void) { int sock; struct sockaddr_pppol2tp addr; sock = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP); if (sock < 0) { perror("socket"); return 1; } addr.sa_family = AF_PPPOX; addr.sa_protocol = PX_PROTO_OL2TP; addr.pppol2tp.pid = 0; addr.pppol2tp.fd = sock; addr.pppol2tp.addr.sin_family = PF_INET; addr.pppol2tp.addr.sin_port = htons(0); addr.pppol2tp.addr.sin_addr.s_addr = inet_addr("192.168.0.1"); addr.pppol2tp.s_tunnel = 1; addr.pppol2tp.s_session = 0; addr.pppol2tp.d_tunnel = 0; addr.pppol2tp.d_session = 0; if (connect(sock, (const struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("connect"); return 1; } return 0; } This program causes the following lockdep warning: ============================================ WARNING: possible recursive locking detected 6.2.0-rc5-00205-gc96618275234 #56 Not tainted -------------------------------------------- repro/8607 is trying to acquire lock: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x2b7/0x11c0 but task is already holding lock: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(sk_lock-AF_PPPOX); lock(sk_lock-AF_PPPOX); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by repro/8607: #0: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30 stack backtrace: CPU: 0 PID: 8607 Comm: repro Not tainted 6.2.0-rc5-00205-gc96618275234 #56 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Call Trace: dump_stack_lvl+0x100/0x178 __lock_acquire.cold+0x119/0x3b9 ? lockdep_hardirqs_on_prepare+0x410/0x410 lock_acquire+0x1e0/0x610 ? l2tp_tunnel_register+0x2b7/0x11c0 ? lock_downgrade+0x710/0x710 ? __fget_files+0x283/0x3e0 lock_sock_nested+0x3a/0xf0 ? l2tp_tunnel_register+0x2b7/0x11c0 l2tp_tunnel_register+0x2b7/0x11c0 ? sprintf+0xc4/0x100 ? l2tp_tunnel_del_work+0x6b0/0x6b0 ? debug_object_deactivate+0x320/0x320 ? lockdep_init_map_type+0x16d/0x7a0 ? lockdep_init_map_type+0x16d/0x7a0 ? l2tp_tunnel_create+0x2bf/0x4b0 ? l2tp_tunnel_create+0x3c6/0x4b0 pppol2tp_connect+0x14e1/0x1a30 ? pppol2tp_put_sk+0xd0/0xd0 ? aa_sk_perm+0x2b7/0xa80 ? aa_af_perm+0x260/0x260 ? bpf_lsm_socket_connect+0x9/0x10 ? pppol2tp_put_sk+0xd0/0xd0 __sys_connect_file+0x14f/0x190 __sys_connect+0x133/0x160 ? __sys_connect_file+0x190/0x190 ? lockdep_hardirqs_on+0x7d/0x100 ? ktime_get_coarse_real_ts64+0x1b7/0x200 ? ktime_get_coarse_real_ts64+0x147/0x200 ? __audit_syscall_entry+0x396/0x500 __x64_sys_connect+0x72/0xb0 do_syscall_64+0x38/0xb0 entry_SYSCALL_64_after_hwframe+0x63/0xcd This patch fixes the issue by returning error when a pppol2tp socket itself is passed. Signed-off-by: Shigeru Yoshida --- net/l2tp/l2tp_ppp.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c index db2e584c625e..88d1a339500b 100644 --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -702,11 +702,14 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr, struct l2tp_tunnel_cfg tcfg = { .encap = L2TP_ENCAPTYPE_UDP, }; + int dummy = 0; /* Prevent l2tp_tunnel_register() from trying to set up - * a kernel socket. + * a kernel socket. Also, prevent l2tp_tunnel_register() + * from trying to use pppol2tp socket itself. */ - if (info.fd < 0) { + if (info.fd < 0 || + sock == sockfd_lookup(info.fd, &dummy)) { error = -EBADF; goto end; }