From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 781DEC433FE for ; Mon, 21 Nov 2022 09:01:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230078AbiKUJBC (ORCPT ); Mon, 21 Nov 2022 04:01:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230092AbiKUJAz (ORCPT ); Mon, 21 Nov 2022 04:00:55 -0500 Received: from mail-ed1-x536.google.com (mail-ed1-x536.google.com [IPv6:2a00:1450:4864:20::536]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A93483EB7 for ; Mon, 21 Nov 2022 01:00:53 -0800 (PST) Received: by mail-ed1-x536.google.com with SMTP id f7so15256199edc.6 for ; Mon, 21 Nov 2022 01:00:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=mime-version:message-id:in-reply-to:date:subject:cc:to:from :user-agent:references:from:to:cc:subject:date:message-id:reply-to; bh=Zrgtw0c3wlZA/yLqn73oinTIP8rBDSYjdfY3JiqY95Y=; b=FX92/3g89aBBdGw8DVUZGivQJtvneU1hhd40rtHhxDy5+vjd7eQ0L87fFyeaDv8eYr jWTLHFoyISLLTOyo0qY/XsJZHuNONd2R315irYa7X9+iZDp2gyi8IjLrO8VVxUt0Wbq6 nbN9rZzw8TzlT2pLFC1zrInmaOSK6bFBf2Hbw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=mime-version:message-id:in-reply-to:date:subject:cc:to:from :user-agent:references:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Zrgtw0c3wlZA/yLqn73oinTIP8rBDSYjdfY3JiqY95Y=; b=cISg8JMWIcgoVtWeivacCeU7CeQRMbTPEm8FhH7ijddrQsVa5MqjZ9s28U504yYAbl ckaDs75vSEy7GSO4DfUdFXUKoFnoSjoOj3klkT8aJZRF04rZLiZuhAImibHcoboBwgKa rtvuZYnsDFlFR5CF0OoO4N6tyngofhKnYuUE5ACCGVnk+xQNo16b87edy7CTsU0QotH9 KyY+xrtbod3+5hjI9hQ6EJ1Cvn0xOQ19H/joXTHGq4LPFk0rJRzuqbclBnrfC7wm83C9 HKEMHvfv3R1PlYnqFv2uioukJwmbIeH0LHTWhzK5Q5vQeN2xrEE1WGk21m+hE/bWGl2N l8cQ== X-Gm-Message-State: ANoB5pk4YB2mW18WFjvuhyNDLJfwZjnB2lZ1p1ZbnBW9hYiszOtQ11l6 ZK235JtLnP9gmFiWw9A1gRwMItCKBJOWYw== X-Google-Smtp-Source: AA0mqf4MGMXQsd1mc/MxFUt+u3uLWv4Oy/01mFKD/PLMtVjf08N7BVrEO9u9Jr2/Zin1BUalzVCURQ== X-Received: by 2002:a05:6402:419:b0:461:e82b:bdff with SMTP id q25-20020a056402041900b00461e82bbdffmr14717759edv.370.1669021251799; Mon, 21 Nov 2022 01:00:51 -0800 (PST) Received: from cloudflare.com (79.184.204.15.ipv4.supernova.orange.pl. [79.184.204.15]) by smtp.gmail.com with ESMTPSA id x20-20020a170906805400b007919ba4295esm4791867ejw.216.2022.11.21.01.00.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Nov 2022 01:00:51 -0800 (PST) References: <20221119130317.39158-1-jakub@cloudflare.com> User-agent: mu4e 1.6.10; emacs 27.2 From: Jakub Sitnicki To: Tetsuo Handa Cc: netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Tom Parkin , syzbot+703d9e154b3b58277261@syzkaller.appspotmail.com, syzbot+50680ced9e98a61f7698@syzkaller.appspotmail.com, syzbot+de987172bb74a381879b@syzkaller.appspotmail.com Subject: Re: [PATCH net] l2tp: Don't sleep and disable BH under writer-side sk_callback_lock Date: Mon, 21 Nov 2022 10:00:09 +0100 In-reply-to: Message-ID: <871qpw8ywt.fsf@cloudflare.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Nov 19, 2022 at 10:52 PM +09, Tetsuo Handa wrote: > On 2022/11/19 22:03, Jakub Sitnicki wrote: >> When holding a reader-writer spin lock we cannot sleep. Calling >> setup_udp_tunnel_sock() with write lock held violates this rule, because we >> end up calling percpu_down_read(), which might sleep, as syzbot reports >> [1]: >> >> __might_resched.cold+0x222/0x26b kernel/sched/core.c:9890 >> percpu_down_read include/linux/percpu-rwsem.h:49 [inline] >> cpus_read_lock+0x1b/0x140 kernel/cpu.c:310 >> static_key_slow_inc+0x12/0x20 kernel/jump_label.c:158 >> udp_tunnel_encap_enable include/net/udp_tunnel.h:187 [inline] >> setup_udp_tunnel_sock+0x43d/0x550 net/ipv4/udp_tunnel_core.c:81 >> l2tp_tunnel_register+0xc51/0x1210 net/l2tp/l2tp_core.c:1509 >> pppol2tp_connect+0xcdc/0x1a10 net/l2tp/l2tp_ppp.c:723 >> >> Trim the writer-side critical section for sk_callback_lock down to the >> minimum, so that it covers only operations on sk_user_data. > > This patch does not look correct. > > Since l2tp_validate_socket() checks that sk->sk_user_data == NULL with > sk->sk_callback_lock held, you need to call rcu_assign_sk_user_data(sk, tunnel) > before releasing sk->sk_callback_lock. You're right. v2 posted: https://lore.kernel.org/netdev/20221121085426.21315-1-jakub@cloudflare.com/