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 B0787C433EF for ; Mon, 31 Jan 2022 01:08:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357277AbiAaBIz (ORCPT ); Sun, 30 Jan 2022 20:08:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230269AbiAaBIy (ORCPT ); Sun, 30 Jan 2022 20:08:54 -0500 Received: from mail-ej1-x629.google.com (mail-ej1-x629.google.com [IPv6:2a00:1450:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10D09C061714; Sun, 30 Jan 2022 17:08:54 -0800 (PST) Received: by mail-ej1-x629.google.com with SMTP id d10so37525957eje.10; Sun, 30 Jan 2022 17:08:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=/d/1F9joOfYdE7Tjusc7U3ydwf04rVdyD/sh2o80Dvc=; b=Uo+HMKLcTJoLkKZKJE3EMGnbXY5T/7RWOMYM1Y3RdkVoaTqfiP9EADcaJ25rlD7TSY 3GQCxrmUGSSOlJy2IAP9jwp61J1d86GqacffCGJwigPeN+Qk1TA4jTwaLVOuuvT9+0si L80dMWdrqgFRTKtucEpH878HQegKZPNGs4KaDvXI/kzU7kqfDh9xuUgZHuEzfhb2G5Vn S7y9Dc5CLRMIybMNCsRbpdOYKdz/Z8G49rf9nRJ9v9JoL7WxxdAKckoopI0x6tjADyAS AsZXxDvATj0ecqXslDxo8IKjHVvQYxYFL870Yqhj6cpIDa2UChsOlEVvoO7tYRJEnqKv 7KvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=/d/1F9joOfYdE7Tjusc7U3ydwf04rVdyD/sh2o80Dvc=; b=J/EMmpFVmBi3kEPlQu9oSVG/EIWlCeEhLFE2k82lt8Y1x+8gv0FpS8OwL9hssAcPGi kMumkkXe1En0HP4ee7N5IBVOJVFB97e2aTfSnaAJsvcIC+19TeQ9mklo0PMJtL3oswOO R1NOYkTFR8Fuy2PzWMzdNb+PDoDM+6aifyta9R328MtyADw2LZsKsBTIL1YbEMiTC3fB IQnO4LouSUM+WEBo0Nz6M7prADACLtchpz3lQrO+O+QoR8U1mID/9BSLCODjPg54qsce TjpmTnJNmJrjJbylneRgfzanyFXtL/iWNlzU/J806OeUE4B0q+7CRAuoY5zJk9i8h/al frKQ== X-Gm-Message-State: AOAM533N1k5DV4YFMDlbKoo6ho22hnGyjS9NM5U6DB5CU93DjCAvVbfS vV+YfzfMe4prYWN0Y5nyM9hLnvSnIXBENFIkiNU= X-Google-Smtp-Source: ABdhPJxZPWV48CWMD0JcMgf4O5xrEqYDt3d6X2bH4YPowqblA+Awh3Kk37P4F4PPZjRpu3XFXV9ss0C39yYenx+HzeA= X-Received: by 2002:a17:907:7ea4:: with SMTP id qb36mr14642721ejc.551.1643591332413; Sun, 30 Jan 2022 17:08:52 -0800 (PST) MIME-Version: 1.0 References: <159db05f-539c-fe29-608b-91b036588033@molgen.mpg.de> <3534d781-7d01-b42a-8974-0b1c367946f0@molgen.mpg.de> <04a597dc-64aa-57e6-f7fb-17bd2ec58159@molgen.mpg.de> <20220130174421.GS4285@paulmck-ThinkPad-P17-Gen-1> In-Reply-To: <20220130174421.GS4285@paulmck-ThinkPad-P17-Gen-1> From: Zhouyi Zhou Date: Mon, 31 Jan 2022 09:08:40 +0800 Message-ID: Subject: Re: BUG: Kernel NULL pointer dereference on write at 0x00000000 (rtmsg_ifinfo_build_skb) To: "Paul E. McKenney" Cc: Paul Menzel , Josh Triplett , rcu , LKML , "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Thank Paul for joining us! On Mon, Jan 31, 2022 at 1:44 AM Paul E. McKenney wrote= : > > On Sun, Jan 30, 2022 at 09:24:44PM +0800, Zhouyi Zhou wrote: > > Dear Paul > > > > On Sun, Jan 30, 2022 at 4:19 PM Paul Menzel wro= te: > > > > > > Dear Zhouyi, > > > > > > > > > Am 30.01.22 um 01:21 schrieb Zhouyi Zhou: > > > > > > > Thank you for your instructions, I learned a lot from this process. > > > > > > Same on my end. > > > > > > > On Sun, Jan 30, 2022 at 12:52 AM Paul Menzel wrote: > > > > > > >> Am 29.01.22 um 03:23 schrieb Zhouyi Zhou: > > > >> > > > >>> I don't have an IBM machine, but I tried to analyze the problem u= sing > > > >>> my x86_64 kvm virtual machine, I can't reproduce the bug using my > > > >>> x86_64 kvm virtual machine. > > > >> > > > >> No idea, if it=E2=80=99s architecture specific. > > > >> > > > >>> I saw the panic is caused by registration of sit device (A sit de= vice > > > >>> is a type of virtual network device that takes our IPv6 traffic, > > > >>> encapsulates/decapsulates it in IPv4 packets, and sends/receives = it > > > >>> over the IPv4 Internet to another host) > > > >>> > > > >>> sit device is registered in function sit_init_net: > > > >>> 1895 static int __net_init sit_init_net(struct net *net) > > > >>> 1896 { > > > >>> 1897 struct sit_net *sitn =3D net_generic(net, sit_net_id)= ; > > > >>> 1898 struct ip_tunnel *t; > > > >>> 1899 int err; > > > >>> 1900 > > > >>> 1901 sitn->tunnels[0] =3D sitn->tunnels_wc; > > > >>> 1902 sitn->tunnels[1] =3D sitn->tunnels_l; > > > >>> 1903 sitn->tunnels[2] =3D sitn->tunnels_r; > > > >>> 1904 sitn->tunnels[3] =3D sitn->tunnels_r_l; > > > >>> 1905 > > > >>> 1906 if (!net_has_fallback_tunnels(net)) > > > >>> 1907 return 0; > > > >>> 1908 > > > >>> 1909 sitn->fb_tunnel_dev =3D alloc_netdev(sizeof(struct ip= _tunnel), "sit0", > > > >>> 1910 NET_NAME_UNKNOWN, > > > >>> 1911 ipip6_tunnel_setup); > > > >>> 1912 if (!sitn->fb_tunnel_dev) { > > > >>> 1913 err =3D -ENOMEM; > > > >>> 1914 goto err_alloc_dev; > > > >>> 1915 } > > > >>> 1916 dev_net_set(sitn->fb_tunnel_dev, net); > > > >>> 1917 sitn->fb_tunnel_dev->rtnl_link_ops =3D &sit_link_ops; > > > >>> 1918 /* FB netdevice is special: we have one, and only one= per netns. > > > >>> 1919 * Allowing to move it to another netns is clearly un= safe. > > > >>> 1920 */ > > > >>> 1921 sitn->fb_tunnel_dev->features |=3D NETIF_F_NETNS_LOCA= L; > > > >>> 1922 > > > >>> 1923 err =3D register_netdev(sitn->fb_tunnel_dev); > > > >>> register_netdev on line 1923 will call if_nlmsg_size indirectly. > > > >>> > > > >>> On the other hand, the function that calls the paniced strlen is = if_nlmsg_size: > > > >>> (gdb) disassemble if_nlmsg_size > > > >>> Dump of assembler code for function if_nlmsg_size: > > > >>> 0xffffffff81a0dc20 <+0>: nopl 0x0(%rax,%rax,1) > > > >>> 0xffffffff81a0dc25 <+5>: push %rbp > > > >>> 0xffffffff81a0dc26 <+6>: push %r15 > > > >>> 0xffffffff81a0dd04 <+228>: je 0xffffffff81a0de20 > > > >>> 0xffffffff81a0dd0a <+234>: mov 0x10(%rbp),%rdi > > > >>> ... > > > >>> =3D> 0xffffffff81a0dd0e <+238>: callq 0xffffffff817532d0 <= strlen> > > > >>> 0xffffffff81a0dd13 <+243>: add $0x10,%eax > > > >>> 0xffffffff81a0dd16 <+246>: movslq %eax,%r12 > > > >> > > > >> Excuse my ignorance, would that look the same for ppc64le? > > > >> Unfortunately, I didn=E2=80=99t save the problematic `vmlinuz` fil= e, but on a > > > >> current build (without rcutorture) I have the line below, where st= rlen > > > >> shows up. > > > >> > > > >> (gdb) disassemble if_nlmsg_size > > > >> [=E2=80=A6] > > > >> 0xc000000000f7f82c <+332>: bl 0xc000000000a10e30 > > > >> [=E2=80=A6] > > > >> > > > >>> and the C code for 0xffffffff81a0dd0e is following (line 524): > > > >>> 515 static size_t rtnl_link_get_size(const struct net_device *= dev) > > > >>> 516 { > > > >>> 517 const struct rtnl_link_ops *ops =3D dev->rtnl_link_ops= ; > > > >>> 518 size_t size; > > > >>> 519 > > > >>> 520 if (!ops) > > > >>> 521 return 0; > > > >>> 522 > > > >>> 523 size =3D nla_total_size(sizeof(struct nlattr)) + /* IF= LA_LINKINFO */ > > > >>> 524 nla_total_size(strlen(ops->kind) + 1); /* IFLA= _INFO_KIND */ > > > >> > > > >> How do I connect the disassemby output with the corresponding line= ? > > > > I use "make ARCH=3Dpowerpc CC=3Dpowerpc64le-linux-gnu-gcc-9 > > > > CROSS_COMPILE=3Dpowerpc64le-linux-gnu- -j 16" to cross compile kern= el > > > > for powerpc64le in my Ubuntu 20.04 x86_64. > > > > > > > > gdb-multiarch ./vmlinux > > > > (gdb)disassemble if_nlmsg_size > > > > [...] > > > > 0xc00000000191bf40 <+112>: bl 0xc000000001c28ad0 > > > > [...] > > > > (gdb) break *0xc00000000191bf40 > > > > Breakpoint 1 at 0xc00000000191bf40: file ./include/net/netlink.h, l= ine 1112. > > > > > > > > But in include/net/netlink.h:1112, I can't find the call to strlen > > > > 1110static inline int nla_total_size(int payload) > > > > 1111{ > > > > 1112 return NLA_ALIGN(nla_attr_size(payload)); > > > > 1113} > > > > This may be due to the compiler wrongly encode the debug informatio= n, I guess. > > > > > > `rtnl_link_get_size()` contains: > > > > > > size =3D nla_total_size(sizeof(struct nlattr)) + /* > > > IFLA_LINKINFO */ > > > nla_total_size(strlen(ops->kind) + 1); /* > > > IFLA_INFO_KIND */ > > > > > > Is that inlined(?) and the code at fault? > > Yes, that is inlined! because > > (gdb) disassemble if_nlmsg_size > > Dump of assembler code for function if_nlmsg_size: > > [...] > > 0xc00000000191bf38 <+104>: beq 0xc00000000191c1f0 > > 0xc00000000191bf3c <+108>: ld r3,16(r31) > > 0xc00000000191bf40 <+112>: bl 0xc000000001c28ad0 > > [...] > > (gdb) > > (gdb) break *0xc00000000191bf40 > > Breakpoint 1 at 0xc00000000191bf40: file ./include/net/netlink.h, line = 1112. > > (gdb) break *0xc00000000191bf38 > > Breakpoint 2 at 0xc00000000191bf38: file net/core/rtnetlink.c, line 520= . > > I suggest building your kernel with CONFIG_DEBUG_INFO=3Dy if you are not > already doing so. That gives gdb a lot more information about things > like inlining. I check my .config file, CONFIG_DEBUG_INFO=3Dy is here: linux-next$ grep CONFIG_DEBUG_INFO .config CONFIG_DEBUG_INFO=3Dy Then I invoke "make clean" and rebuild the kernel, the behavior of gdb and vmlinux remain unchanged, sorry for that I am trying to reproduce the bug on my bare metal x86_64 machines in the coming days, and am also trying to work with Mr Menzel after he comes back to the office. Thanks Zhouyi > > Thanx, Paul > > > > >>> But ops is assigned the value of sit_link_ops in function sit_ini= t_net > > > >>> line 1917, so I guess something must happened between the calls. > > > >>> > > > >>> Do we have KASAN in IBM machine? would KASAN help us find out wha= t > > > >>> happened in between? > > > >> > > > >> Unfortunately, KASAN is not support on Power, I have, as far as I = can > > > >> see. From `arch/powerpc/Kconfig`: > > > >> > > > >> select HAVE_ARCH_KASAN if PPC32 && PPC_= PAGE_SHIFT <=3D 14 > > > >> select HAVE_ARCH_KASAN_VMALLOC if PPC32 && PPC_= PAGE_SHIFT <=3D 14 > > > >> > > > > en, agree, I invoke "make menuconfig ARCH=3Dpowerpc > > > > CC=3Dpowerpc64le-linux-gnu-gcc-9 CROSS_COMPILE=3Dpowerpc64le-linux-= gnu- -j > > > > 16", I can't find KASAN under Memory Debugging, I guess we should f= ind > > > > the bug by bisecting instead. > > > > > > I do not know, if it is a regression, as it was the first time I trie= d > > > to run a Linux kernel built with rcutorture on real hardware. > > I tried to add some debug statements to the kernel to locate the bug > > more accurately, you can try it when you're not busy in the future, > > or just ignore it if the following patch looks not very effective ;-) > > diff --git a/net/core/dev.c b/net/core/dev.c > > index 1baab07820f6..969ac7c540cc 100644 > > --- a/net/core/dev.c > > +++ b/net/core/dev.c > > @@ -9707,6 +9707,9 @@ int register_netdevice(struct net_device *dev) > > * Prevent userspace races by waiting until the network > > * device is fully setup before sending notifications. > > */ > > + if (dev->rtnl_link_ops) > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", dev->rtnl_link_= ops, > > + dev->rtnl_link_ops->kind, __FUNCTION__); > > if (!dev->rtnl_link_ops || > > dev->rtnl_link_state =3D=3D RTNL_LINK_INITIALIZED) > > rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U, GFP_KERNEL); > > @@ -9788,6 +9791,9 @@ int register_netdev(struct net_device *dev) > > > > if (rtnl_lock_killable()) > > return -EINTR; > > + if (dev->rtnl_link_ops) > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", dev->rtnl_link_= ops, > > + dev->rtnl_link_ops->kind, __FUNCTION__); > > err =3D register_netdevice(dev); > > rtnl_unlock(); > > return err; > > diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c > > index e476403231f0..e08986ae6238 100644 > > --- a/net/core/rtnetlink.c > > +++ b/net/core/rtnetlink.c > > @@ -520,6 +520,8 @@ static size_t rtnl_link_get_size(const struct > > net_device *dev) > > if (!ops) > > return 0; > > > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", ops, > > + ops->kind, __FUNCTION__); > > size =3D nla_total_size(sizeof(struct nlattr)) + /* IFLA_LINKINFO = */ > > nla_total_size(strlen(ops->kind) + 1); /* IFLA_INFO_KIND *= / > > > > @@ -1006,6 +1008,9 @@ static size_t rtnl_proto_down_size(const struct > > net_device *dev) > > static noinline size_t if_nlmsg_size(const struct net_device *dev, > > u32 ext_filter_mask) > > { > > + if (dev->rtnl_link_ops) > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", dev->rtnl_link= _ops, > > + dev->rtnl_link_ops->kind, __FUNCTION__); > > return NLMSG_ALIGN(sizeof(struct ifinfomsg)) > > + nla_total_size(IFNAMSIZ) /* IFLA_IFNAME */ > > + nla_total_size(IFALIASZ) /* IFLA_IFALIAS */ > > @@ -3825,7 +3830,9 @@ struct sk_buff *rtmsg_ifinfo_build_skb(int type, > > struct net_device *dev, > > struct net *net =3D dev_net(dev); > > struct sk_buff *skb; > > int err =3D -ENOBUFS; > > - > > + if (dev->rtnl_link_ops) > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", dev->rtnl_link_= ops, > > + dev->rtnl_link_ops->kind, __FUNCTION__); > > skb =3D nlmsg_new(if_nlmsg_size(dev, 0), flags); > > if (skb =3D=3D NULL) > > goto errout; > > @@ -3861,7 +3868,9 @@ static void rtmsg_ifinfo_event(int type, struct > > net_device *dev, > > > > if (dev->reg_state !=3D NETREG_REGISTERED) > > return; > > - > > + if (dev->rtnl_link_ops) > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", dev->rtnl_link= _ops, > > + dev->rtnl_link_ops->kind, __FUNCTION__); > > skb =3D rtmsg_ifinfo_build_skb(type, dev, change, event, flags, ne= w_nsid, > > new_ifindex); > > if (skb) > > @@ -3871,6 +3880,9 @@ static void rtmsg_ifinfo_event(int type, struct > > net_device *dev, > > void rtmsg_ifinfo(int type, struct net_device *dev, unsigned int chang= e, > > gfp_t flags) > > { > > + if (dev->rtnl_link_ops) > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", dev->rtnl_link= _ops, > > + dev->rtnl_link_ops->kind, __FUNCTION__); > > rtmsg_ifinfo_event(type, dev, change, rtnl_get_event(0), flags, > > NULL, 0); > > } > > diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c > > index c0b138c20992..fa5b2725811c 100644 > > --- a/net/ipv6/sit.c > > +++ b/net/ipv6/sit.c > > @@ -1919,6 +1919,8 @@ static int __net_init sit_init_net(struct net *ne= t) > > * Allowing to move it to another netns is clearly unsafe. > > */ > > sitn->fb_tunnel_dev->features |=3D NETIF_F_NETNS_LOCAL; > > - > > + printk(KERN_INFO "%lx IFLA_INFO_KIND %s %s\n", > > + sitn->fb_tunnel_dev->rtnl_link_ops, > > + sitn->fb_tunnel_dev->rtnl_link_ops->kind, __FUNCTION__); > > err =3D register_netdev(sitn->fb_tunnel_dev); > > if (err) > > goto err_reg_dev; > > > > > > >>> Hope I can be of more helpful. > > > >> > > > >> Some distributions support multi-arch, so they easily allow > > > >> crosscompiling for different architectures. > > > > I use "make ARCH=3Dpowerpc CC=3Dpowerpc64le-linux-gnu-gcc-9 > > > > CROSS_COMPILE=3Dpowerpc64le-linux-gnu- -j 16" to cross compile kern= el > > > > for powerpc64le in my Ubuntu 20.04 x86_64. But I can't boot the > > > > compiled kernel using "qemu-system-ppc64le -M pseries -nographic -s= mp > > > > 4 -net none -m 4G -kernel arch/powerpc/boot/zImage". I will continu= e > > > > to explore it. > > > > > > Oh, that does not sound good. But I have not tried that in a long tim= e > > > either. It=E2=80=99s a separate issue, but maybe some of the PPC > > > maintainers/folks could help. > > I will do further research on this later. > > > > Thanks for your time > > Kind regards > > Zhouyi > > > > > > > > > Kind regards, > > > > > > Paul