| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <265b1953-36b4-6a65-1a36-67a61248f27f@molgen.mpg.de>
Date: Mon, 21 Feb 2022 12:17:40 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Zhouyi Zhou <zhouzhouyi@...il.com>,
"Paul E. McKenney" <paulmck@...nel.org>,
Josh Triplett <josh@...htriplett.org>, rcu@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
Nick Desaulniers <ndesaulniers@...gle.com>,
llvm@...ts.linux.dev, Fangrui Song <i@...kray.me>
Subject: Re: BUG: Kernel NULL pointer dereference on write at 0x00000000
(rtmsg_ifinfo_build_skb)
[Cc: +Fangrui]
Dear Nathan,
Am 17.02.22 um 02:16 schrieb Nathan Chancellor:
> On Wed, Feb 16, 2022 at 02:19:51PM +0100, Paul Menzel wrote:
>> [Cc: +LLVM/clang build support folks]
[…]
>> To recap: On a ppc64le machine, building Linux in Ubuntu 21.10 with *llvm*
>> and *clang* 1:13.0-53~exp1
>>
>> $ clang --version
>> Ubuntu clang version 13.0.0-2
>> Target: powerpc64le-unknown-linux-gnu
>> Thread model: posix
>> InstalledDir: /usr/bin
>>
>> results in a segmentation fault, while it works when building with GCC.
>>
>> $ gcc --version
>> gcc (Ubuntu 11.2.0-7ubuntu2) 11.2.0
>
> Thank you for keying us in. I am going to have a bit of a brain dump
> here based on the information I have uncovered after a couple of hours
> of debugging.
>
> TL;DR: It seems like something is broken with __read_mostly + ld.lld
> before 14.0.0.
>
> My initial reproduction steps (boot-qemu.sh comes from
> https://github.com/ClangBuiltLinux/boot-utils):
>
> $ clang --version
> clang version 13.0.1 (Fedora 13.0.1-1.fc37)
> Target: x86_64-redhat-linux-gnu
> Thread model: posix
> InstalledDir: /usr/bin
>
> $ powerpc64le-linux-gnu-as --version
> GNU assembler version 2.37-2.fc36
> Copyright (C) 2021 Free Software Foundation, Inc.
> This program is free software; you may redistribute it under the terms of
> the GNU General Public License version 3 or later.
> This program has absolutely no warranty.
> This assembler was configured for a target of `powerpc64le-linux-gnu'.
>
> $ curl -LSso .config https://lore.kernel.org/all/f41550c7-26c0-cf81-7de9-aa924434a565@molgen.mpg.de/3-linux-5.17-rc4-rcu-dev-config.txt
>
> $ scripts/config --set-val INITRAMFS_SOURCE '""'
>
> $ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- LLVM=1 LLVM_IAS=0 all
>
> $ boot-qemu.sh -a ppc64le -k . -t 45s
> QEMU location: /usr/bin
>
> QEMU version: QEMU emulator version 6.2.0 (qemu-6.2.0-5.fc37)
>
> + timeout --foreground 45s stdbuf -oL -eL qemu-system-ppc64 -initrd \
> /home/nathan/cbl/github/boot-utils-ro/images/ppc64le/rootfs.cpio -device \
> ipmi-bmc-sim,id=bmc0 -device isa-ipmi-bt,bmc=bmc0,irq=10 -L \
> /home/nathan/cbl/github/boot-utils-ro/images/ppc64le/ -bios skiboot.lid \
> -machine powernv8 -display none -kernel \
> /home/nathan/cbl/src/linux/arch/powerpc/boot/zImage.epapr -m 2G \
> -nodefaults -serial mon:stdio
> ...
> [ 1.478028][ T1] BUG: Kernel NULL pointer dereference on read at 0x00000000
> [ 1.478630][ T1] Faulting instruction address: 0xc00000000090bee0
> [ 1.479521][ T1] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 1.480036][ T1] LE PAGE_SIZE=64K MMU=Hash PREEMPT SMP NR_CPUS=16 NUMA PowerNV
> [ 1.480853][ T1] Modules linked in:
> [ 1.481265][ T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc4-00001-gfa15c7cb550f #1
> [ 1.481967][ T1] NIP: c00000000090bee0 LR: c000000000d96b60 CTR: c0000000000d5b4c
> [ 1.482596][ T1] REGS: c000000007443330 TRAP: 0380 Not tainted (5.17.0-rc4-00001-gfa15c7cb550f)
> [ 1.483305][ T1] MSR: 9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE> CR: 22800a87 XER: 00000000
> [ 1.484277][ T1] CFAR: c000000000d96b5c IRQMASK: 0
> [ 1.484277][ T1] GPR00: c000000000d96b54 c0000000074435d0 c0000000028bc600 0000000000000000
> [ 1.484277][ T1] GPR04: ffffffffffffffff ffffffffff1ea558 ffffffffff1ebfe4 c00000000261ae88
> [ 1.484277][ T1] GPR08: 0000000000000003 0000000000000004 c00000000261ae88 0000000000000000
> [ 1.484277][ T1] GPR12: 0000000000800000 c000000002a60000 c000000000012518 0000000000000000
> [ 1.484277][ T1] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [ 1.484277][ T1] GPR20: 0000000000000000 c0000000027bff80 0000000000000cc0 0000000000000000
> [ 1.484277][ T1] GPR24: 0000000000000010 0000000000000000 0000000000000000 0000000000000000
> [ 1.484277][ T1] GPR28: c0000000028fcfd8 c000000007b83000 0000000000000000 c0000000074435d0
> [ 1.490325][ T1] NIP [c00000000090bee0] strlen+0x10/0x30
> [ 1.490788][ T1] LR [c000000000d96b60] if_nlmsg_size+0x2b0/0x390
> [ 1.491319][ T1] Call Trace:
> [ 1.491573][ T1] [c0000000074435d0] [c000000000d96b54] if_nlmsg_size+0x2a4/0x390 (unreliable)
> [ 1.492291][ T1] [c000000007443680] [c000000000d96790] rtmsg_ifinfo_build_skb+0x80/0x1a0
> [ 1.492958][ T1] [c000000007443740] [c000000000d97590] rtmsg_ifinfo+0x70/0xd0
> [ 1.493559][ T1] [c000000007443790] [c000000000d7d528] register_netdevice+0x5d8/0x670
> [ 1.494205][ T1] [c000000007443820] [c000000000d7d94c] register_netdev+0x4c/0x80
> [ 1.494823][ T1] [c000000007443850] [c000000000f826d8] sit_init_net+0x1b8/0x200
> [ 1.495426][ T1] [c0000000074438d0] [c000000000d63b5c] ops_init+0x14c/0x1c0
> [ 1.496014][ T1] [c000000007443930] [c000000000d6314c] register_pernet_operations+0xec/0x1e0
> [ 1.496716][ T1] [c000000007443990] [c000000000d633d0] register_pernet_device+0x60/0xd0
> [ 1.497372][ T1] [c0000000074439e0] [c000000002085194] sit_init+0x54/0x160
> [ 1.497950][ T1] [c000000007443a70] [c000000000011c58] do_one_initcall+0x108/0x3e0
> [ 1.498573][ T1] [c000000007443c70] [c000000002006190] do_initcall_level+0xe4/0x1c4
> [ 1.499219][ T1] [c000000007443cc0] [c00000000200604c] do_initcalls+0x84/0xe4
> [ 1.499799][ T1] [c000000007443d40] [c000000002005da8] kernel_init_freeable+0x160/0x1ec
> [ 1.500444][ T1] [c000000007443da0] [c00000000001254c] kernel_init+0x3c/0x270
> [ 1.501042][ T1] [c000000007443e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
> [ 1.501721][ T1] Instruction dump:
> [ 1.502202][ T1] eb81ffe0 7c0803a6 4e800020 00000000 00000000 00000000 60000000 60000000
> [ 1.502934][ T1] 3883ffff 60000000 60000000 60000000 <8ca40001> 28050000 4082fff8 7c632050
> [ 1.504028][ T1] ---[ end trace 0000000000000000 ]---
> ...
>
> First thing was figuring out where the NULL pointer dereference happens,
> which appears to the "strlen(ops->kind)" in rtnl_link_get_size():
>
> 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 */
>
> which I confirmed some really rudimentary printk debugging:
>
> [ 1.476862][ T1] nathan: rtnl_link_get_size(): name: sit0, ops: c0000000028fcfd8, ops->kind: (null)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 710da8a36729..c8d928e83aec 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -520,6 +520,9 @@ static size_t rtnl_link_get_size(const struct net_device *dev)
> if (!ops)
> return 0;
>
> + pr_err("nathan: %s(): name: %s, ops: %px, ops->kind: %s\n", __func__,
> + dev->name, ops, ops->kind);
> +
> size = nla_total_size(sizeof(struct nlattr)) + /* IFLA_LINKINFO */
> nla_total_size(strlen(ops->kind) + 1); /* IFLA_INFO_KIND */
>
>
> Okay... how did sit0 end up with a NULL kind...? It is very clearly
> defined as "sit":
>
> 1830 static struct rtnl_link_ops sit_link_ops __read_mostly = {
> 1831 .kind = "sit",
>
> Adding some more debug prints to net/ipv6/sit.c:
>
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index c0b138c20992..7b9edbed2fcd 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -1920,6 +1920,12 @@ static int __net_init sit_init_net(struct net *net)
> */
> sitn->fb_tunnel_dev->features |= NETIF_F_NETNS_LOCAL;
>
> + pr_err("nathan: %s(): &sit_link_ops: %px\n", __func__, &sit_link_ops);
> + pr_err("nathan: %s(): sit_link_ops.kind: %s\n", __func__, sit_link_ops.kind);
> + pr_err("nathan: %s(): sit_link_ops.maxtype: %u\n", __func__, sit_link_ops.maxtype);
> + pr_err("nathan: %s(): sitn->fb_tunnel_dev->rtnl_link_ops: %px\n", __func__, sitn->fb_tunnel_dev->rtnl_link_ops);
> + pr_err("nathan: %s(): sitn->fb_tunnel_dev->rtnl_link_ops->kind: %s\n", __func__, sitn->fb_tunnel_dev->rtnl_link_ops->kind);
> +
> err = register_netdev(sitn->fb_tunnel_dev);
> if (err)
> goto err_reg_dev;
>
> reveals:
>
> [ 1.471920][ T1] sit: nathan: sit_init_net(): &sit_link_ops: c0000000028fcfd8
> [ 1.472534][ T1] sit: nathan: sit_init_net(): sit_link_ops.kind: (null)
> [ 1.473088][ T1] sit: nathan: sit_init_net(): sit_link_ops.maxtype: 20
> [ 1.473639][ T1] sit: nathan: sit_init_net(): sitn->fb_tunnel_dev->rtnl_link_ops: c0000000028fcfd8
> [ 1.474370][ T1] sit: nathan: sit_init_net(): sitn->fb_tunnel_dev->rtnl_link_ops->kind: (null)
>
> This is super bizarre, as the maxtype member appears to have the correct
> value, but how is kind's initial getting dropped on the floor?
>
> Removing the __read_mostly annotation "fixes" it:
>
> [ 1.481708][ T1] sit: nathan: sit_init_net(): &sit_link_ops: c0000000027d3f60
> [ 1.482319][ T1] sit: nathan: sit_init_net(): sit_link_ops.kind: sit
> [ 1.482878][ T1] sit: nathan: sit_init_net(): sit_link_ops.maxtype: 20
> [ 1.483429][ T1] sit: nathan: sit_init_net(): sitn->fb_tunnel_dev->rtnl_link_ops: c0000000027d3f60
> [ 1.484174][ T1] sit: nathan: sit_init_net(): sitn->fb_tunnel_dev->rtnl_link_ops->kind: sit
> ...
> Linux version 5.17.0-rc4-00001-g956f02ad5c31-dirty (nathan@...-fedora.archlinux-ax161) (clang version 13.0.1 (Fedora 13.0.1-1.fc37), LLD 13.0.1) #2 SMP PREEMPT Wed Feb 16 13:29:49 MST 2022
> ...
>
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index 7b9edbed2fcd..f109c7a0233b 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -70,7 +70,7 @@ static void ipip6_tunnel_setup(struct net_device *dev);
> static void ipip6_dev_free(struct net_device *dev);
> static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst,
> __be32 *v4dst);
> -static struct rtnl_link_ops sit_link_ops __read_mostly;
> +static struct rtnl_link_ops sit_link_ops;
>
> static unsigned int sit_net_id __read_mostly;
> struct sit_net {
> @@ -1827,7 +1827,7 @@ static void ipip6_dellink(struct net_device *dev, struct list_head *head)
> unregister_netdevice_queue(dev, head);
> }
>
> -static struct rtnl_link_ops sit_link_ops __read_mostly = {
> +static struct rtnl_link_ops sit_link_ops = {
> .kind = "sit",
> .maxtype = IFLA_IPTUN_MAX,
> .policy = ipip6_policy,
>
> Switching to ld.bfd also resolves it:
>
> [ 1.470405][ T1] sit: nathan: sit_init_net(): &sit_link_ops: c0000000028acfd8
> [ 1.471016][ T1] sit: nathan: sit_init_net(): sit_link_ops.kind: sit
> [ 1.471534][ T1] sit: nathan: sit_init_net(): sit_link_ops.maxtype: 20
> [ 1.472062][ T1] sit: nathan: sit_init_net(): sitn->fb_tunnel_dev->rtnl_link_ops: c0000000028acfd8
> [ 1.472790][ T1] sit: nathan: sit_init_net(): sitn->fb_tunnel_dev->rtnl_link_ops->kind: sit
> ...
> Linux version 5.17.0-rc4-00001-g956f02ad5c31 (nathan@...-fedora.archlinux-ax161) (clang version 13.0.1 (Fedora 13.0.1-1.fc37), GNU ld version 2.37-2.fc36) #3 SMP PREEMPT Wed Feb 16 13:33:42 MST 2022
> ...
>
> I tested with ToT LLVM (or at least, close to it, since there is an
> unrelated ld.lld regression there) and I could not reproduce it there,
> so I did a reverse bisect to see what commit fixes this issue in LLVM 14
> and I landed on:
>
> commit 55c14d6dbfd8e7b86c15d2613fea3490078e2ae4
> Author: Fangrui Song <i@...kray.me>
> Date: Thu Nov 25 14:12:34 2021 -0800
>
> [ELF] Simplify DynamicSection content computation. NFC
>
> The new code computes the content twice, but avoides the tricky
> std::function<uint64_t()>. Removed 13KiB code in a Release build.
>
> lld/ELF/SyntheticSections.cpp | 117 ++++++++++++++++--------------------------
> lld/ELF/SyntheticSections.h | 12 +----
> 2 files changed, 44 insertions(+), 85 deletions(-)
>
> That's... interesting, given that commit title says No Functional
> Change, even though there clearly is one. That commit has a couple
> mentions of PowerPC synthetic sections, so it is possible that the
> new content calculation lines up with ld.bfd?
>
> I am not really sure where to go from here, as I don't fully understand
> what the problem was before that LLD change. I'll see if I can do some
> more investigation tomorrow (unless someone wants to beat me to it ;)
Thank you for looking into this, and sharing your analysis.
I built LLVM/clang from the master branch, rebuilt, but can still
reproduce this.
$ git clone --depth=1 https://github.com/llvm/llvm-project.git
$ cd llvm-project/
$ git log --oneline
41cb504b7 [mlir][linalg][bufferize][NFC] Move interface impl to
Linalg Transforms
$ mkdir build
$ cd build
$ cmake -DLLVM_ENABLE_PROJECTS=clang -G "Unix Makefiles"
-DCMAKE_BUILD_TYPE=Release -DLLVM_INSTALL_UTILS=ON
-DCMAKE_INSTALL_PREFIX=/scratch/local2/llvm ../llvm
$ make -j20
$ make -j20 clang-check
$ make install
$ /scratch/local2/llvm/bin/clang --version
clang version 15.0.0 (https://github.com/llvm/llvm-project.git
41cb504b7c4b18ac15830107431a0c1eec73a6b2)
Target: powerpc64le-unknown-linux-gnu
Thread model: posix
InstalledDir: /scratch/local2/llvm/bin
Then build Linux after `make clean` with `/scratch/local2/llvm/bin` in
the path.
$ LLVM=1 LLVM_IAS=0 eatmydata make -j20
$ qemu-system-ppc64 -enable-kvm -nographic -smp cores=1,threads=1
-net none -enable-kvm -M pseries -nodefaults -device spapr-vscsi -serial
stdio -m 512 -kernel /dev/shm/linux/vmlinux -append
"debug_boot_weak_hash panic=-1 console=ttyS0
rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot
rcupdate.rcu_task_stall_timeout=30000 rcupdate.rcu_self_test=1
rcutorture.onoff_interval=1000 rcutorture.onoff_holdoff=30
rcutorture.n_barrier_cbs=4 rcutorture.stat_interval=15
rcutorture.shutdown_secs=420 rcutorture.test_no_idle_hz=1
rcutorture.verbose=1"
[…]
Preparing to boot Linux version 5.17.0-rc5-00178-ga4b9a8fb20e7
(pmenzel@...ghafenberlinbrandenburgwillybrandt.molgen.mpg.de) (clang
version 15.0.0 (https://github.com/llvm/llvm-project.git
41cb504b7c4b18ac15830107431a0c1eec73a6b2), LLD 13.0.0) #29 SMP PREEMPT
Mon Feb 21 10:58:54 CET 2022
[…]
[ 0.465889][ T1] BUG: Kernel NULL pointer dereference on read
at 0x00000000
[ 0.466749][ T1] Faulting instruction address: 0xc0000000008fc300
[ 0.467507][ T1] Oops: Kernel access of bad area, sig: 11 [#1]
[…]
Kind regards,
Paul
Powered by blists - more mailing lists