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 27FB7C32771 for ; Fri, 19 Aug 2022 10:37:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245098AbiHSKhM (ORCPT ); Fri, 19 Aug 2022 06:37:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348227AbiHSKhM (ORCPT ); Fri, 19 Aug 2022 06:37:12 -0400 Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A8EEF438B for ; Fri, 19 Aug 2022 03:37:11 -0700 (PDT) Received: by mail-ed1-x52e.google.com with SMTP id r4so5131170edi.8 for ; Fri, 19 Aug 2022 03:37:10 -0700 (PDT) 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; bh=QsEaufN8elOkxyYkBSs1ElvXCpjDNX+kzGQIG065aiI=; b=pK811Wz2NzMerPkeJY4198aIAqKVaWZ1H16jf7gVn1Ng0Koof6BvZm3rbqVS/qqG3v APzC+FPyKmloxStZyCsla4PmKDiXwOYypkZncW8Wx2nxk9l3Ci0rg74ung3Xc9bL72gB hCicgx9f57nrb+MGjmkZi0/4qg/JXF+xEb39Y= 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; bh=QsEaufN8elOkxyYkBSs1ElvXCpjDNX+kzGQIG065aiI=; b=ABZC0WK2UcB9EwX+kmmO2u09p2EXRpTZNrNyI55fUO13OvMePVNfZdUWJri2hIAUUH OavixxnJr4bE4O3Ecz1RFyquuzwVGqR2XzL3ACQ343zIqCciyzUeQ/HVu8LqBAOGXu/w xt1ahiPSXqXzuhL+/Y+dZ0G1E+9x1o/H5jNBeA7rZqLq2BMBXpUC2NntdR6/xzxI7KB1 l31jXPCjiSCGatmc4LRFxp8L14ttKs3u/GWgEFxjdctQUDgYc0Q38DqFyWGgwcv6pGKK b0IwUwzA2dlM8N2y/FhMCvPmyG7R8KXYUq2cEMa487HALwEe2y5vWpxhv24IhcL0dgTR CyOA== X-Gm-Message-State: ACgBeo2Wy99vb4UxfmuK1uQWSiRAghKd0R+w1clz8XoSYnNMw8dVUgv9 XNrozWxAe5yQtHDy+T4yUZ2rQQ== X-Google-Smtp-Source: AA6agR4W6boYrOmdIRkqk9iAVlfej5ZekjZxH8/6zt+ERgWxXJ3wxbfjN7s48ol1stIPS+jk7qqehQ== X-Received: by 2002:aa7:d856:0:b0:445:e147:e014 with SMTP id f22-20020aa7d856000000b00445e147e014mr5640783eds.425.1660905429522; Fri, 19 Aug 2022 03:37:09 -0700 (PDT) Received: from cloudflare.com (79.184.200.53.ipv4.supernova.orange.pl. [79.184.200.53]) by smtp.gmail.com with ESMTPSA id 27-20020a170906329b00b0073c0b87ba34sm1840601ejw.198.2022.08.19.03.37.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Aug 2022 03:37:09 -0700 (PDT) References: <20220815023343.295094-1-liujian56@huawei.com> <20220815023343.295094-2-liujian56@huawei.com> <871qtc1u9e.fsf@cloudflare.com> <2ad6173f254f4842b1abaeaf9a7a1e7d@huawei.com> User-agent: mu4e 1.6.10; emacs 27.2 From: Jakub Sitnicki To: "liujian (CE)" Cc: "john.fastabend@gmail.com" , "edumazet@google.com" , "davem@davemloft.net" , "yoshfuji@linux-ipv6.org" , "dsahern@kernel.org" , "kuba@kernel.org" , "pabeni@redhat.com" , "andrii@kernel.org" , "mykolal@fb.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "martin.lau@linux.dev" , "song@kernel.org" , "yhs@fb.com" , "kpsingh@kernel.org" , "sdf@google.com" , "haoluo@google.com" , "jolsa@kernel.org" , "shuah@kernel.org" , "bpf@vger.kernel.org" Subject: Re: [PATCH bpf-next 1/2] sk_msg: Keep reference on socket file while wait_memory Date: Fri, 19 Aug 2022 12:34:42 +0200 In-reply-to: <2ad6173f254f4842b1abaeaf9a7a1e7d@huawei.com> Message-ID: <87wnb4zfhn.fsf@cloudflare.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Aug 19, 2022 at 10:01 AM GMT, liujian (CE) wrote: >> -----Original Message----- >> From: Jakub Sitnicki [mailto:jakub@cloudflare.com] >> Sent: Friday, August 19, 2022 4:39 PM >> To: liujian (CE) ; john.fastabend@gmail.com; >> edumazet@google.com >> Cc: davem@davemloft.net; yoshfuji@linux-ipv6.org; dsahern@kernel.org; >> kuba@kernel.org; pabeni@redhat.com; andrii@kernel.org; mykolal@fb.com; >> ast@kernel.org; daniel@iogearbox.net; martin.lau@linux.dev; >> song@kernel.org; yhs@fb.com; kpsingh@kernel.org; sdf@google.com; >> haoluo@google.com; jolsa@kernel.org; shuah@kernel.org; >> bpf@vger.kernel.org >> Subject: Re: [PATCH bpf-next 1/2] sk_msg: Keep reference on socket file >> while wait_memory >> >> On Mon, Aug 15, 2022 at 10:33 AM +08, Liu Jian wrote: >> > Fix the below NULL pointer dereference: >> > >> > [ 14.471200] Call Trace: >> > [ 14.471562] >> > [ 14.471882] lock_acquire+0x245/0x2e0 >> > [ 14.472416] ? remove_wait_queue+0x12/0x50 >> > [ 14.473014] ? _raw_spin_lock_irqsave+0x17/0x50 >> > [ 14.473681] _raw_spin_lock_irqsave+0x3d/0x50 >> > [ 14.474318] ? remove_wait_queue+0x12/0x50 >> > [ 14.474907] remove_wait_queue+0x12/0x50 >> > [ 14.475480] sk_stream_wait_memory+0x20d/0x340 >> > [ 14.476127] ? do_wait_intr_irq+0x80/0x80 >> > [ 14.476704] do_tcp_sendpages+0x287/0x600 >> > [ 14.477283] tcp_bpf_push+0xab/0x260 >> > [ 14.477817] tcp_bpf_sendmsg_redir+0x297/0x500 >> > [ 14.478461] ? __local_bh_enable_ip+0x77/0xe0 >> > [ 14.479096] tcp_bpf_send_verdict+0x105/0x470 >> > [ 14.479729] tcp_bpf_sendmsg+0x318/0x4f0 >> > [ 14.480311] sock_sendmsg+0x2d/0x40 >> > [ 14.480822] ____sys_sendmsg+0x1b4/0x1c0 >> > [ 14.481390] ? copy_msghdr_from_user+0x62/0x80 >> > [ 14.482048] ___sys_sendmsg+0x78/0xb0 >> > [ 14.482580] ? vmf_insert_pfn_prot+0x91/0x150 >> > [ 14.483215] ? __do_fault+0x2a/0x1a0 >> > [ 14.483738] ? do_fault+0x15e/0x5d0 >> > [ 14.484246] ? __handle_mm_fault+0x56b/0x1040 >> > [ 14.484874] ? lock_is_held_type+0xdf/0x130 >> > [ 14.485474] ? find_held_lock+0x2d/0x90 >> > [ 14.486046] ? __sys_sendmsg+0x41/0x70 >> > [ 14.486587] __sys_sendmsg+0x41/0x70 >> > [ 14.487105] ? intel_pmu_drain_pebs_core+0x350/0x350 >> > [ 14.487822] do_syscall_64+0x34/0x80 >> > [ 14.488345] entry_SYSCALL_64_after_hwframe+0x63/0xcd >> > >> > The test scene as following flow: >> > thread1 thread2 >> > ----------- --------------- >> > tcp_bpf_sendmsg >> > tcp_bpf_send_verdict >> > tcp_bpf_sendmsg_redir sock_close >> > tcp_bpf_push_locked __sock_release >> > tcp_bpf_push //inet_release >> > do_tcp_sendpages sock->ops->release >> > sk_stream_wait_memory // tcp_close >> > sk_wait_event sk->sk_prot->close >> > release_sock(__sk); >> > *** >> > >> > lock_sock(sk); >> > __tcp_close >> > sock_orphan(sk) >> > sk->sk_wq = NULL >> > release_sock >> > **** >> > lock_sock(__sk); >> > remove_wait_queue(sk_sleep(sk), &wait); >> > sk_sleep(sk) >> > //NULL pointer dereference >> > &rcu_dereference_raw(sk->sk_wq)->wait >> > >> > While waiting for memory in thread1, the socket is released with its >> > wait queue because thread2 has closed it. This caused by >> > tcp_bpf_send_verdict didn't increase the f_count of psock->sk_redir- >> >sk_socket->file in thread1. >> >> I'm not sure about this approach. Keeping a closed sock file alive, just so we >> can wakeup from sleep, seems like wasted effort. >> >> __tcp_close sets sk->sk_shutdown = RCV_SHUTDOWN | SEND_SHUTDOWN. >> So we will return from sk_stream_wait_memory via the do_error path. >> >> SEND_SHUTDOWN might be set because socket got closed and orphaned - >> dead and detached from its file, like in this case. >> >> So, IMHO, we should check if SOCK_DEAD flag is set on wakeup due to >> SEND_SHUTDOWN in sk_stream_wait_memory, before accessing the wait >> queue. >> >> [...] > As jakub's approach, this problem can be solved. > > diff --git a/include/net/sock.h b/include/net/sock.h > index a7273b289188..a3dab7140f1e 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -1998,6 +1998,8 @@ static inline void sk_set_socket(struct sock *sk, struct socket *sock) > static inline wait_queue_head_t *sk_sleep(struct sock *sk) > { > BUILD_BUG_ON(offsetof(struct socket_wq, wait) != 0); > + if (sock_flag(sk, SOCK_DEAD)) > + return NULL; > return &rcu_dereference_raw(sk->sk_wq)->wait; > } > /* Detach socket from process context. > diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c > index 9860bb9a847c..da1be17d0b19 100644 > --- a/kernel/sched/wait.c > +++ b/kernel/sched/wait.c > @@ -51,6 +51,8 @@ void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry > { > unsigned long flags; > > + if (wq_head == NULL) > + return; > spin_lock_irqsave(&wq_head->lock, flags); > __remove_wait_queue(wq_head, wq_entry); > spin_unlock_irqrestore(&wq_head->lock, flags); I don't know if we want to change the contract for sk_sleep() remove_wait_queue() so that they accept dead sockets or nulls. How about just: diff --git a/net/core/stream.c b/net/core/stream.c index ccc083cdef23..1105057ce00a 100644 --- a/net/core/stream.c +++ b/net/core/stream.c @@ -159,7 +159,8 @@ int sk_stream_wait_memory(struct sock *sk, long *timeo_p) *timeo_p = current_timeo; } out: - remove_wait_queue(sk_sleep(sk), &wait); + if (!sock_flag(sk, SOCK_DEAD)) + remove_wait_queue(sk_sleep(sk), &wait); return err; do_error: