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 AC932C433F5 for ; Sun, 30 Jan 2022 17:44:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355753AbiA3RoZ (ORCPT ); Sun, 30 Jan 2022 12:44:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41528 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355752AbiA3RoY (ORCPT ); Sun, 30 Jan 2022 12:44:24 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CECA1C061714; Sun, 30 Jan 2022 09:44:23 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E0A9F6128E; Sun, 30 Jan 2022 17:44:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41191C340E4; Sun, 30 Jan 2022 17:44:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643564662; bh=A2/P/hRhICdFkzpp7TrQlj84u1wxKK9vsR3UDwVYsfU=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=lAgbcGpTyv7Oj7kgwOg8ks6DGZsioF6XE40cd61r7Ri0r0upso4fI0zRuItNHGJUX +N3iXA8cVO0BqkKieges6WJkYIYGgw9cytdmDH1kO2U3uhN/Ee5wDSMgjdLCxwbu74 DST/v/CMhHTZ8RNY2KL8TWMq+1FUuEiqaLTuJnd5lUqbWsMKeSrAoTBV8YzI9LBYmA IyBZQbkSavqje8swdNMDY+zBdu4KIGZGhr1x3vM8pDL10MhpxPNFsJ7c3LEg41ZEBV QE7Uit7aZ7lAuNFAJwZr3yAwD/mF878scQyX+1JVKWHhX27XGLnh+GvPtR9RAyW1MQ 5MhgM2z1TSwvQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id F3A575C043B; Sun, 30 Jan 2022 09:44:21 -0800 (PST) Date: Sun, 30 Jan 2022 09:44:21 -0800 From: "Paul E. McKenney" To: Zhouyi Zhou Cc: Paul Menzel , Josh Triplett , rcu , LKML , "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org Subject: Re: BUG: Kernel NULL pointer dereference on write at 0x00000000 (rtmsg_ifinfo_build_skb) Message-ID: <20220130174421.GS4285@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org 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 wrote: > > > > 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 using > > >>> my x86_64 kvm virtual machine, I can't reproduce the bug using my > > >>> x86_64 kvm virtual machine. > > >> > > >> No idea, if it’s architecture specific. > > >> > > >>> I saw the panic is caused by registration of sit device (A sit device > > >>> 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 = net_generic(net, sit_net_id); > > >>> 1898 struct ip_tunnel *t; > > >>> 1899 int err; > > >>> 1900 > > >>> 1901 sitn->tunnels[0] = sitn->tunnels_wc; > > >>> 1902 sitn->tunnels[1] = sitn->tunnels_l; > > >>> 1903 sitn->tunnels[2] = sitn->tunnels_r; > > >>> 1904 sitn->tunnels[3] = sitn->tunnels_r_l; > > >>> 1905 > > >>> 1906 if (!net_has_fallback_tunnels(net)) > > >>> 1907 return 0; > > >>> 1908 > > >>> 1909 sitn->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "sit0", > > >>> 1910 NET_NAME_UNKNOWN, > > >>> 1911 ipip6_tunnel_setup); > > >>> 1912 if (!sitn->fb_tunnel_dev) { > > >>> 1913 err = -ENOMEM; > > >>> 1914 goto err_alloc_dev; > > >>> 1915 } > > >>> 1916 dev_net_set(sitn->fb_tunnel_dev, net); > > >>> 1917 sitn->fb_tunnel_dev->rtnl_link_ops = &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 unsafe. > > >>> 1920 */ > > >>> 1921 sitn->fb_tunnel_dev->features |= NETIF_F_NETNS_LOCAL; > > >>> 1922 > > >>> 1923 err = 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 > > >>> ... > > >>> => 0xffffffff81a0dd0e <+238>: callq 0xffffffff817532d0 > > >>> 0xffffffff81a0dd13 <+243>: add $0x10,%eax > > >>> 0xffffffff81a0dd16 <+246>: movslq %eax,%r12 > > >> > > >> Excuse my ignorance, would that look the same for ppc64le? > > >> Unfortunately, I didn’t save the problematic `vmlinuz` file, but on a > > >> current build (without rcutorture) I have the line below, where strlen > > >> shows up. > > >> > > >> (gdb) disassemble if_nlmsg_size > > >> […] > > >> 0xc000000000f7f82c <+332>: bl 0xc000000000a10e30 > > >> […] > > >> > > >>> 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 = dev->rtnl_link_ops; > > >>> 518 size_t size; > > >>> 519 > > >>> 520 if (!ops) > > >>> 521 return 0; > > >>> 522 > > >>> 523 size = nla_total_size(sizeof(struct nlattr)) + /* IFLA_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=powerpc CC=powerpc64le-linux-gnu-gcc-9 > > > CROSS_COMPILE=powerpc64le-linux-gnu- -j 16" to cross compile kernel > > > 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, line 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 information, I guess. > > > > `rtnl_link_get_size()` contains: > > > > size = 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=y if you are not already doing so. That gives gdb a lot more information about things like inlining. Thanx, Paul > > >>> But ops is assigned the value of sit_link_ops in function sit_init_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 what > > >>> 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 <= 14 > > >> select HAVE_ARCH_KASAN_VMALLOC if PPC32 && PPC_PAGE_SHIFT <= 14 > > >> > > > en, agree, I invoke "make menuconfig ARCH=powerpc > > > CC=powerpc64le-linux-gnu-gcc-9 CROSS_COMPILE=powerpc64le-linux-gnu- -j > > > 16", I can't find KASAN under Memory Debugging, I guess we should find > > > the bug by bisecting instead. > > > > I do not know, if it is a regression, as it was the first time I tried > > 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 == 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 = 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 = 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 = dev_net(dev); > struct sk_buff *skb; > int err = -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 = nlmsg_new(if_nlmsg_size(dev, 0), flags); > if (skb == NULL) > goto errout; > @@ -3861,7 +3868,9 @@ static void rtmsg_ifinfo_event(int type, struct > net_device *dev, > > if (dev->reg_state != 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 = rtmsg_ifinfo_build_skb(type, dev, change, event, flags, new_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 change, > 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 *net) > * Allowing to move it to another netns is clearly unsafe. > */ > sitn->fb_tunnel_dev->features |= 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 = 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=powerpc CC=powerpc64le-linux-gnu-gcc-9 > > > CROSS_COMPILE=powerpc64le-linux-gnu- -j 16" to cross compile kernel > > > for powerpc64le in my Ubuntu 20.04 x86_64. But I can't boot the > > > compiled kernel using "qemu-system-ppc64le -M pseries -nographic -smp > > > 4 -net none -m 4G -kernel arch/powerpc/boot/zImage". I will continue > > > to explore it. > > > > Oh, that does not sound good. But I have not tried that in a long time > > either. It’s 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