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 X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73F49C4338F for ; Wed, 11 Aug 2021 19:46:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39E736023E for ; Wed, 11 Aug 2021 19:46:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231444AbhHKTq0 (ORCPT ); Wed, 11 Aug 2021 15:46:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229991AbhHKTqW (ORCPT ); Wed, 11 Aug 2021 15:46:22 -0400 Received: from mail-yb1-xb2b.google.com (mail-yb1-xb2b.google.com [IPv6:2607:f8b0:4864:20::b2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CC81C061765 for ; Wed, 11 Aug 2021 12:45:58 -0700 (PDT) Received: by mail-yb1-xb2b.google.com with SMTP id z128so6841547ybc.10 for ; Wed, 11 Aug 2021 12:45:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=rmCZfgibO0w4qM0h5z9GUKC+BABdJ5Xz7PCci/uX+uc=; b=bQNINJdh8XyFjAH1nodbu4ve7ZJa9ey6urBIbSxjDFSLPyrCRZN0IrF3YOFltFWMmQ /3yqc24HsOOoMyPHPdmCuvIzT2NNQbqhQVbOpt9RfoqDH3o+ycuuHt2lK70vVvCsgXPn dBadmLbwDpoU4h0Ea8rDkauNlCqmwmDkbjj+8j2X2dFh9BOV3XWKN1uaAybLK5OKA+nu kmTBFu4nuq7e3I3PoGPQUcIb7oQCMkhFUJKWqQ4228jIEKbbSwYlorPeR/Q5MeSCkjSl nFrr9pA83WmGz+StD+aRoaMdBvvx9UMhQroBa8+X0gxmfsCyhpryoR9ETe3sH2nxr/TJ 6KPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rmCZfgibO0w4qM0h5z9GUKC+BABdJ5Xz7PCci/uX+uc=; b=m1mZcMhEZ3dht9I6cLduKiCkWXUVHtNIy0R0Dfa22rbH4wKTUBlBnXynvYIswNX8pG dqyDFApnU7oNC3/hIsDc3UMl6xQiyPvX7NkqqqXGd7PTsIOLgVzW59Kxt9hSPt5dyckm 4zM0h7HGP8miD6JA5PjQ3Uh5zDgSZZbIFAE0rwkLBGE40KsnWbo5HfeMDSpvE7MbGP6q 6PWhKYieiP7+ih6keRqm3JDWiwzIInPjXbQEPJ6W7z+MNPtAN+ceOfwqW7v9UGaXcRqK lhBHKCTo8yqGk+aqM+WVAlhp2e/6E9gp+cWJQjNxTuDdG2IiPe5GhkltF+dO2O1hqkwT 4wIg== X-Gm-Message-State: AOAM5316gTQtKXUtgjNN7DtEs/fgBVPC1ir6oNKMISREXOZrOFk+dAGx r0DK53HVKyPXtgR4TcQUzaNbEDJOxZXeBqGn9vuYxA== X-Google-Smtp-Source: ABdhPJyEelXsYoHGDhlf/xVnYTD//bTmbhRiScNl85Op27cZUES9xv/ElmA4bMcLTy+Z9uCKBLcZiJAkDFKcxY8e+7w= X-Received: by 2002:a25:afcd:: with SMTP id d13mr114441ybj.504.1628711156478; Wed, 11 Aug 2021 12:45:56 -0700 (PDT) MIME-Version: 1.0 References: <20210810094547.1851947-1-eric.dumazet@gmail.com> <20210811182923.GA4027194@roeck-us.net> <20210811183256.GA4139434@roeck-us.net> In-Reply-To: <20210811183256.GA4139434@roeck-us.net> From: Eric Dumazet Date: Wed, 11 Aug 2021 21:45:45 +0200 Message-ID: Subject: Re: [PATCH net] net: igmp: fix data-race in igmp_ifc_timer_expire() To: Guenter Roeck Cc: Eric Dumazet , "David S . Miller" , Jakub Kicinski , netdev , syzbot Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Time to make mr_ifc_count a 32bit field then :/ On Wed, Aug 11, 2021 at 8:32 PM Guenter Roeck wrote: > > On Wed, Aug 11, 2021 at 11:29:25AM -0700, Guenter Roeck wrote: > > On Tue, Aug 10, 2021 at 02:45:47AM -0700, Eric Dumazet wrote: > > > From: Eric Dumazet > > > > > > Fix the data-race reported by syzbot [1] > > > Issue here is that igmp_ifc_timer_expire() can update in_dev->mr_ifc_count > > > while another change just occured from another context. > > > > > > in_dev->mr_ifc_count is only 8bit wide, so the race had little > > > consequences. > > > > > > [1] > > > BUG: KCSAN: data-race in igmp_ifc_event / igmp_ifc_timer_expire > > > > > > write to 0xffff8881051e3062 of 1 bytes by task 12547 on cpu 0: > > > igmp_ifc_event+0x1d5/0x290 net/ipv4/igmp.c:821 > > > igmp_group_added+0x462/0x490 net/ipv4/igmp.c:1356 > > > ____ip_mc_inc_group+0x3ff/0x500 net/ipv4/igmp.c:1461 > > > __ip_mc_join_group+0x24d/0x2c0 net/ipv4/igmp.c:2199 > > > ip_mc_join_group_ssm+0x20/0x30 net/ipv4/igmp.c:2218 > > > do_ip_setsockopt net/ipv4/ip_sockglue.c:1285 [inline] > > > ip_setsockopt+0x1827/0x2a80 net/ipv4/ip_sockglue.c:1423 > > > tcp_setsockopt+0x8c/0xa0 net/ipv4/tcp.c:3657 > > > sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3362 > > > __sys_setsockopt+0x18f/0x200 net/socket.c:2159 > > > __do_sys_setsockopt net/socket.c:2170 [inline] > > > __se_sys_setsockopt net/socket.c:2167 [inline] > > > __x64_sys_setsockopt+0x62/0x70 net/socket.c:2167 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > > > read to 0xffff8881051e3062 of 1 bytes by interrupt on cpu 1: > > > igmp_ifc_timer_expire+0x706/0xa30 net/ipv4/igmp.c:808 > > > call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1419 > > > expire_timers+0x135/0x250 kernel/time/timer.c:1464 > > > __run_timers+0x358/0x420 kernel/time/timer.c:1732 > > > run_timer_softirq+0x19/0x30 kernel/time/timer.c:1745 > > > __do_softirq+0x12c/0x26e kernel/softirq.c:558 > > > invoke_softirq kernel/softirq.c:432 [inline] > > > __irq_exit_rcu+0x9a/0xb0 kernel/softirq.c:636 > > > sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100 > > > asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 > > > console_unlock+0x8e8/0xb30 kernel/printk/printk.c:2646 > > > vprintk_emit+0x125/0x3d0 kernel/printk/printk.c:2174 > > > vprintk_default+0x22/0x30 kernel/printk/printk.c:2185 > > > vprintk+0x15a/0x170 kernel/printk/printk_safe.c:392 > > > printk+0x62/0x87 kernel/printk/printk.c:2216 > > > selinux_netlink_send+0x399/0x400 security/selinux/hooks.c:6041 > > > security_netlink_send+0x42/0x90 security/security.c:2070 > > > netlink_sendmsg+0x59e/0x7c0 net/netlink/af_netlink.c:1919 > > > sock_sendmsg_nosec net/socket.c:703 [inline] > > > sock_sendmsg net/socket.c:723 [inline] > > > ____sys_sendmsg+0x360/0x4d0 net/socket.c:2392 > > > ___sys_sendmsg net/socket.c:2446 [inline] > > > __sys_sendmsg+0x1ed/0x270 net/socket.c:2475 > > > __do_sys_sendmsg net/socket.c:2484 [inline] > > > __se_sys_sendmsg net/socket.c:2482 [inline] > > > __x64_sys_sendmsg+0x42/0x50 net/socket.c:2482 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > > > value changed: 0x01 -> 0x02 > > > > > > Reported by Kernel Concurrency Sanitizer on: > > > CPU: 1 PID: 12539 Comm: syz-executor.1 Not tainted 5.14.0-rc4-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > > > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > > > Signed-off-by: Eric Dumazet > > > Reported-by: syzbot > > > --- > > > net/ipv4/igmp.c | 21 ++++++++++++++------- > > > 1 file changed, 14 insertions(+), 7 deletions(-) > > > > > > diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c > > > index 6b3c558a4f232652b97a078d48f302864e60a866..a51360087b19845a28408c827032e08dabf99838 100644 > > > --- a/net/ipv4/igmp.c > > > +++ b/net/ipv4/igmp.c > > > @@ -803,10 +803,17 @@ static void igmp_gq_timer_expire(struct timer_list *t) > > > static void igmp_ifc_timer_expire(struct timer_list *t) > > > { > > > struct in_device *in_dev = from_timer(in_dev, t, mr_ifc_timer); > > > + u8 mr_ifc_count; > > > > > > igmpv3_send_cr(in_dev); > > > - if (in_dev->mr_ifc_count) { > > > - in_dev->mr_ifc_count--; > > > +restart: > > > + mr_ifc_count = READ_ONCE(in_dev->mr_ifc_count); > > > + > > > + if (mr_ifc_count) { > > > + if (cmpxchg(&in_dev->mr_ifc_count, > > > > Unfortunately riscv only supports 4-byte and 8-byte cmpxchg(), > > so this results in build errors. > > > > Building riscv:defconfig ... failed > > -------------- > > Error log: > > In file included from : > > net/ipv4/igmp.c: In function 'igmp_ifc_timer_expire': > > include/linux/compiler_types.h:328:45: error: call to '__compiletime_assert_547' declared with attribute error: BUILD_BUG failed > > > > Also: > > Building arm:allmodconfig ... failed > -------------- > Error log: > arm-linux-gnueabi-ld: net/ipv4/igmp.o: in function `igmp_ifc_timer_expire': > igmp.c:(.text+0x9b44): undefined reference to `__bad_cmpxchg' > make[1]: *** [Makefile:1176: vmlinux] Error 1 > make: *** [Makefile:220: __sub-make] Error 2 > > Building xtensa:allmodconfig ... failed > -------------- > Error log: > xtensa-linux-ld: net/ipv4/igmp.o: in function `igmp_gq_timer_expire': > igmp.c:(.text+0x4d4c): undefined reference to `__cmpxchg_called_with_bad_pointer' > xtensa-linux-ld: net/ipv4/igmp.o: in function `igmp_ifc_timer_expire': > igmp.c:(.text+0x4dad): undefined reference to `__cmpxchg_called_with_bad_pointer' > > Guenter