Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756823AbdIHSqx (ORCPT ); Fri, 8 Sep 2017 14:46:53 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:34379 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756294AbdIHSqv (ORCPT ); Fri, 8 Sep 2017 14:46:51 -0400 X-Google-Smtp-Source: ADKCNb7NXmMQ8wn9QLtj8pFG5+MjoncCYgXlUOXIVf4HXGD28GPvsokZ0MFqFPE3wmnFbV/RRpgOFw== Message-ID: <1504896409.15310.83.camel@edumazet-glaptop3.roam.corp.google.com> Subject: Re: WARNING: CPU: 2 PID: 4277 at lib/refcount.c:186 From: Eric Dumazet To: Cong Wang Cc: Shankara Pailoor , LKML , syzkaller , David Miller , Alexey Kuznetsov , Hideaki YOSHIFUJI , Linux Kernel Network Developers Date: Fri, 08 Sep 2017 11:46:49 -0700 In-Reply-To: References:

Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5752 Lines: 129 On Fri, 2017-09-08 at 10:21 -0700, Cong Wang wrote: > (Cc'ing netdev) > > On Fri, Sep 8, 2017 at 5:59 AM, Shankara Pailoor wrote: > > Hi, > > > > I found a warning while fuzzing with Syzkaller on linux 4.13-rc7 on > > x86_64. The full stack trace is below: > > > > WARNING: CPU: 2 PID: 4277 at lib/refcount.c:186 > > refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:186 > > Kernel panic - not syncing: panic_on_warn set ... > > > > CPU: 2 PID: 4277 Comm: syz-executor0 Not tainted 4.13.0-rc7 #3 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > > Ubuntu-1.8.2-1ubuntu1 04/01/2014 > > Call Trace: > > > > __dump_stack lib/dump_stack.c:16 [inline] > > dump_stack+0xf7/0x1aa lib/dump_stack.c:52 > > panic+0x1ae/0x3a7 kernel/panic.c:180 > > __warn+0x1c4/0x1d9 kernel/panic.c:541 > > report_bug+0x211/0x2d0 lib/bug.c:183 > > fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:190 > > do_trap_no_signal arch/x86/kernel/traps.c:224 [inline] > > do_trap+0x260/0x390 arch/x86/kernel/traps.c:273 > > do_error_trap+0x118/0x340 arch/x86/kernel/traps.c:310 > > do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:323 > > invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:846 > > RIP: 0010:refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:186 > > RSP: 0018:ffff88006e006b60 EFLAGS: 00010286 > > RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000 > > RDX: 0000000000000026 RSI: 1ffff1000dc00d2c RDI: ffffed000dc00d60 > > RBP: ffff88006e006bf0 R08: 0000000000000001 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1000dc00d6d > > R13: 00000000ffffffff R14: 0000000000000001 R15: ffff88006ce9d340 > > refcount_dec_and_test+0x1a/0x20 lib/refcount.c:211 > > reqsk_put+0x71/0x2b0 include/net/request_sock.h:123 > > tcp_v4_rcv+0x259e/0x2e20 net/ipv4/tcp_ipv4.c:1729 > > ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216 > > NF_HOOK include/linux/netfilter.h:248 [inline] > > ip_local_deliver+0x1ce/0x6d0 net/ipv4/ip_input.c:257 > > dst_input include/net/dst.h:477 [inline] > > ip_rcv_finish+0x8db/0x19c0 net/ipv4/ip_input.c:397 > > NF_HOOK include/linux/netfilter.h:248 [inline] > > ip_rcv+0xc3f/0x17d0 net/ipv4/ip_input.c:488 > > __netif_receive_skb_core+0x1fb7/0x31f0 net/core/dev.c:4298 > > __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4336 > > process_backlog+0x1c5/0x6d0 net/core/dev.c:5102 > > napi_poll net/core/dev.c:5499 [inline] > > net_rx_action+0x6d3/0x14a0 net/core/dev.c:5565 > > __do_softirq+0x2cb/0xb2d kernel/softirq.c:284 > > do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:898 > > > > do_softirq.part.16+0x63/0x80 kernel/softirq.c:328 > > do_softirq kernel/softirq.c:176 [inline] > > __local_bh_enable_ip+0x84/0x90 kernel/softirq.c:181 > > local_bh_enable include/linux/bottom_half.h:31 [inline] > > rcu_read_unlock_bh include/linux/rcupdate.h:705 [inline] > > ip_finish_output2+0x8ad/0x1360 net/ipv4/ip_output.c:231 > > ip_finish_output+0x74e/0xb80 net/ipv4/ip_output.c:317 > > NF_HOOK_COND include/linux/netfilter.h:237 [inline] > > ip_output+0x1cc/0x850 net/ipv4/ip_output.c:405 > > dst_output include/net/dst.h:471 [inline] > > ip_local_out+0x95/0x160 net/ipv4/ip_output.c:124 > > ip_queue_xmit+0x8c6/0x1810 net/ipv4/ip_output.c:504 > > tcp_transmit_skb+0x1963/0x3320 net/ipv4/tcp_output.c:1123 > > tcp_send_ack.part.35+0x38c/0x620 net/ipv4/tcp_output.c:3575 > > tcp_send_ack+0x49/0x60 net/ipv4/tcp_output.c:3545 > > tcp_rcv_synsent_state_process net/ipv4/tcp_input.c:5795 [inline] > > tcp_rcv_state_process+0x4876/0x4b60 net/ipv4/tcp_input.c:5930 > > tcp_v4_do_rcv+0x58a/0x820 net/ipv4/tcp_ipv4.c:1483 > > sk_backlog_rcv include/net/sock.h:907 [inline] > > __release_sock+0x124/0x360 net/core/sock.c:2223 > > release_sock+0xa4/0x2a0 net/core/sock.c:2715 > > inet_wait_for_connect net/ipv4/af_inet.c:557 [inline] > > __inet_stream_connect+0x671/0xf00 net/ipv4/af_inet.c:643 > > inet_stream_connect+0x58/0xa0 net/ipv4/af_inet.c:682 > > SYSC_connect+0x204/0x470 net/socket.c:1628 > > SyS_connect+0x24/0x30 net/socket.c:1609 > > entry_SYSCALL_64_fastpath+0x18/0xad > > RIP: 0033:0x451e59 > > RSP: 002b:00007f474843fc08 EFLAGS: 00000216 ORIG_RAX: 000000000000002a > > RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 0000000000451e59 > > RDX: 0000000000000010 RSI: 0000000020002000 RDI: 0000000000000007 > > RBP: 0000000000000046 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000216 R12: 0000000000000000 > > R13: 00007ffc040a0f8f R14: 00007f47484409c0 R15: 0000000000000000 > > > > > > > > > > I found that the following program is able to reproduce the warning: > > > > > > Pastebin: https://pastebin.com/B75BdYKz > > > > Here are my configs: https://pastebin.com/zRYCXbak > > > > Regards, > > Shankara > > Sweet, thanks for the report, I will have a look. It seems one reqsk_put(req); is missing, but that would lead to a memory leak, not a double reqsk_put(req) :/ ( Same fix is needed for IPv6 ) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a63486afa7a7e7b4dce88b65bc27cfa872a3ba2f..d9416b5162bc1bdd1acd34fcb4da21cb6b62d0ae 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1669,9 +1669,9 @@ int tcp_v4_rcv(struct sk_buff *skb) */ sock_hold(sk); refcounted = true; - if (tcp_filter(sk, skb)) - goto discard_and_relse; - nsk = tcp_check_req(sk, skb, req, false); + nsk = NULL; + if (!tcp_filter(sk, skb)) + nsk = tcp_check_req(sk, skb, req, false); if (!nsk) { reqsk_put(req); goto discard_and_relse;