Message-ID: <02ce3f503df3446ef1fcfa9338fa5e42b952b13f.camel@redhat.com>
Date: Tue, 09 May 2023 10:10:33 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: "t.feng" <fengtao40@...wei.com>, netdev@...r.kernel.org, 
 lucien.xin@...il.com, luwei32@...wei.com, kuba@...nel.org,
 edumazet@...gle.com,  davem@...emloft.net
Cc: yanan@...wei.com, fw@...len.de
Subject: Re: [PATCH] ipvlan:Fix out-of-bounds caused by unclear skb->cb

Hi,

The patch idea LGTM, but there a few formal things that IMHO should be
adjusted, please see below.

On Mon, 2023-05-08 at 16:47 +0800, t.feng wrote:
> If skb enqueue the qdisc, fq_skb_cb(skb)->time_to_send is changed which
> is actually skb->cb, and IPCB(skb_in)->opt will be used in
> __ip_options_echo. It is possible that memcpy is out of bounds and lead
> to stack overflow.
> We should clear skb->cb before ip_local_out or ip6_local_out.
> 
> Stack info:
> crash on stable-5.10(reproduce in kasan kernel).
> ------------[ cut here ]------------

IIRC the above separator can introduce issues with some patch
management tools, please drop it here and below.

> [ 2203.651571] BUG: KASAN: stack-out-of-bounds in
> __ip_options_echo+0x589/0x800
> [ 2203.653327] Write of size 4 at addr ffff88811a388f27 by task
> swapper/3/0
> 
> [ 2203.655460] CPU: 3 PID: 0 Comm: swapper/3 Kdump: loaded Not tainted
> 5.10.0-60.18.0.50.h856.kasan.eulerosv2r11.x86_64 #1
> [ 2203.655466] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS rel-1.10.2-0-g5f4c7b1-20181220_000000-szxrtosci10000 04/01/2014
> [ 2203.655475] Call Trace:
> [ 2203.655481]  <IRQ>
> [ 2203.655501]  dump_stack+0x9c/0xd3
> [ 2203.655514]  print_address_description.constprop.0+0x19/0x170
> [ 2203.655522]  ? __ip_options_echo+0x589/0x800
> [ 2203.655530]  __kasan_report.cold+0x6c/0x84
> [ 2203.655569]  ? resolve_normal_ct+0x301/0x430 [nf_conntrack]
> [ 2203.655576]  ? __ip_options_echo+0x589/0x800

IMHO it's better if you drop the irrelevant entries - those including 
' ? ' - so that the backtrace is smaller and easier to read.

> [ 2203.655586]  kasan_report+0x3a/0x50
> [ 2203.655594]  check_memory_region+0xfd/0x1f0
> [ 2203.655601]  memcpy+0x39/0x60
> [ 2203.655608]  __ip_options_echo+0x589/0x800
> [ 2203.655616]  ? ip_options_build+0x390/0x390
> [ 2203.655628]  ? _raw_spin_trylock+0x91/0xe0
> [ 2203.655635]  ? _raw_spin_lock_bh+0xe0/0xe0
> [ 2203.655647]  ? icmp_global_allow+0x9d/0x120
> [ 2203.655654]  __icmp_send+0x59a/0x960
> [ 2203.655662]  ? icmpv4_global_allow+0x90/0x90
> [ 2203.655675]  ? nf_nat_cleanup_conntrack+0xe0/0xe0 [nf_nat]
> [ 2203.655702]  ? tcp_print_conntrack+0xb0/0xb0 [nf_conntrack]
> [ 2203.655709]  ? memset+0x20/0x50
> [ 2203.655719]  ? nf_nat_setup_info+0x2fb/0x480 [nf_nat]
> [ 2203.655729]  ? get_unique_tuple+0x390/0x390 [nf_nat]
> [ 2203.655735]  ? tcp_mt+0x456/0x550
> [ 2203.655747]  ? ipt_do_table+0x776/0xa40 [ip_tables]
> [ 2203.655755]  nf_send_unreach+0x129/0x3d0 [nf_reject_ipv4]
> [ 2203.655763]  reject_tg+0x77/0x1bf [ipt_REJECT]
> [ 2203.655772]  ipt_do_table+0x691/0xa40 [ip_tables]
> [ 2203.655783]  ? ip_tables_net_init+0x20/0x20 [ip_tables]
> [ 2203.655794]  ? nf_nat_icmp_reply_translation+0x380/0x380 [nf_nat]
> [ 2203.655804]  ? nf_nat_ipv4_local_fn+0x1ba/0x290 [nf_nat]
> [ 2203.655812]  ? iptable_filter_net_pre_exit+0x50/0x50 [iptable_filter]
> [ 2203.655821]  nf_hook_slow+0x69/0x100
> [ 2203.655828]  __ip_local_out+0x21e/0x2b0
> [ 2203.655836]  ? ip_finish_output+0x190/0x190
> [ 2203.655842]  ? ip_route_output_flow+0x114/0x1b0
> [ 2203.655850]  ? ip_forward_options+0x330/0x330
> [ 2203.655857]  ip_local_out+0x28/0x90
> [ 2203.655868]  ipvlan_process_v4_outbound+0x21e/0x260 [ipvlan]
> [ 2203.655878]  ? ipvlan_process_v6_forward+0x280/0x280 [ipvlan]
> [ 2203.655887]  ? dst_release.part.0+0x3a/0xb0
> [ 2203.655931]  ipvlan_xmit_mode_l3+0x3bd/0x400 [ipvlan]
> [ 2203.655942]  ? ipvlan_xmit_mode_l2+0x3a0/0x3a0 [ipvlan]
> [ 2203.655950]  ? skb_network_protocol+0xd5/0x2d0
> [ 2203.655957]  ? skb_crc32c_csum_help+0x50/0x50
> [ 2203.655967]  ipvlan_queue_xmit+0xb3/0x190 [ipvlan]
> [ 2203.655977]  ipvlan_start_xmit+0x2e/0xb0 [ipvlan]
> [ 2203.655984]  xmit_one.constprop.0+0xe1/0x280
> [ 2203.655992]  dev_hard_start_xmit+0x62/0x100
> [ 2203.656000]  sch_direct_xmit+0x215/0x640
> [ 2203.656009]  ? pvclock_clocksource_read+0xf6/0x1d0
> [ 2203.656015]  ? qdisc_free_cb+0x80/0x80
> [ 2203.656022]  ? dequeue_skb+0x1d7/0x810
> [ 2203.656028]  __qdisc_run+0x153/0x1f0
> [ 2203.656035]  ? sch_direct_xmit+0x640/0x640
> [ 2203.656046]  ? netem_dequeue+0x621/0x700 [sch_netem]
> [ 2203.656053]  ? _raw_spin_lock+0x7a/0xd0
> [ 2203.656060]  ? _raw_spin_lock_irq+0xd0/0xd0
> [ 2203.656069]  __dev_queue_xmit+0x77f/0x1030
> [ 2203.656082]  ? netdev_core_pick_tx+0x160/0x160
> [ 2203.656126]  ? stack_trace_consume_entry+0x60/0x90
> [ 2203.656139]  ? pollwake+0x123/0x180
> [ 2203.656159]  ? selinux_peerlbl_enabled+0x81/0x90
> [ 2203.656173]  ip_finish_output2+0x59b/0xc20
> [ 2203.656184]  ? ip_rcv+0xbf/0x1b0
> [ 2203.656195]  ? ip_reply_glue_bits+0x80/0x80
> [ 2203.656206]  ? napi_poll+0x14f/0x420
> [ 2203.656213]  ? __do_softirq+0xfd/0x402
> [ 2203.656220]  ? asm_call_irq_on_stack+0x12/0x20
> [ 2203.656228]  ? do_softirq_own_stack+0x37/0x50
> [ 2203.656235]  ? get_stack_info_noinstr+0x14/0x110
> [ 2203.656244]  __ip_finish_output.part.0+0x318/0x3d0
> [ 2203.656258]  ? ip_finish_output_gso+0x130/0x130
> [ 2203.656277]  ? get_stack_info+0x32/0xa0
> [ 2203.656289]  ? get_stack_info_noinstr+0x14/0x110
> [ 2203.656301]  ? get_stack_info_noinstr+0x14/0x110
> [ 2203.656312]  ip_finish_output+0x168/0x190
> [ 2203.656320]  ip_output+0x12d/0x220
> [ 2203.656327]  ? ip_mc_output+0x500/0x500
> [ 2203.656335]  ? secondary_startup_64_no_verify+0xc2/0xcb
> [ 2203.656343]  ? __ip_finish_output+0xb0/0xb0
> [ 2203.656349]  ? ipv4_dst_check+0x8b/0xb0
> [ 2203.656357]  __ip_queue_xmit+0x392/0x880
> [ 2203.656369]  ? __ip_queue_xmit+0x880/0x880
> [ 2203.656380]  __tcp_transmit_skb+0x1088/0x11c0
> [ 2203.656395]  ? tcp_event_new_data_sent+0x190/0x190
> [ 2203.656402]  ? __tcp_select_window+0x490/0x490
> [ 2203.656407]  ? tcp_trim_head+0x240/0x240
> [ 2203.656414]  ? ipv4_dst_check+0x8b/0xb0
> [ 2203.656421]  ? tcp_retrans_try_collapse+0x58/0x200
> [ 2203.656428]  ? __sk_dst_check+0x7f/0xe0
> [ 2203.656436]  __tcp_retransmit_skb+0x475/0xa30
> [ 2203.656452]  ? tcp_retrans_try_collapse+0x200/0x200
> [ 2203.656465]  ? tcp_mark_skb_lost+0x158/0x1c0
> [ 2203.656477]  ? rb_next+0x1e/0x90
> [ 2203.656484]  ? tcp_timeout_mark_lost+0x1b7/0x230
> [ 2203.656492]  ? bictcp_cwnd_event+0x15/0xa0
> [ 2203.656498]  ? bictcp_state+0x18c/0x1a0
> [ 2203.656505]  tcp_retransmit_skb+0x2d/0x190
> [ 2203.656512]  tcp_retransmit_timer+0x3af/0x9a0
> [ 2203.656519]  tcp_write_timer_handler+0x3ba/0x510
> [ 2203.656529]  tcp_write_timer+0x55/0x180
> [ 2203.656536]  ? tcp_write_timer_handler+0x510/0x510
> [ 2203.656542]  call_timer_fn+0x3f/0x1d0
> [ 2203.656549]  ? tcp_write_timer_handler+0x510/0x510
> [ 2203.656555]  expire_timers+0x160/0x200
> [ 2203.656562]  run_timer_softirq+0x1f4/0x480
> [ 2203.656569]  ? expire_timers+0x200/0x200
> [ 2203.656576]  ? pvclock_clocksource_read+0xf6/0x1d0
> [ 2203.656584]  ? kvm_sched_clock_read+0xd/0x20
> [ 2203.656590]  ? sched_clock+0x5/0x10
> [ 2203.656598]  ? sched_clock_cpu+0x18/0x130
> [ 2203.656606]  __do_softirq+0xfd/0x402
> [ 2203.656613]  asm_call_irq_on_stack+0x12/0x20
> [ 2203.656617]  </IRQ>
> [ 2203.656623]  do_softirq_own_stack+0x37/0x50
> [ 2203.656631]  irq_exit_rcu+0x134/0x1a0
> [ 2203.656639]  sysvec_apic_timer_interrupt+0x36/0x80
> [ 2203.656646]  asm_sysvec_apic_timer_interrupt+0x12/0x20
> [ 2203.656654] RIP: 0010:default_idle+0x13/0x20
> [ 2203.656663] Code: 89 f0 5d 41 5c 41 5d 41 5e c3 cc cc cc cc cc cc cc
> cc cc cc cc cc cc 0f 1f 44 00 00 0f 1f 44 00 00 0f 00 2d 9f 32 57 00 fb
> f4 <c3> cc cc cc cc 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 54 be 08
> [ 2203.656668] RSP: 0018:ffff88810036fe78 EFLAGS: 00000256
> [ 2203.656676] RAX: ffffffffaf2a87f0 RBX: ffff888100360000 RCX:
> ffffffffaf290191
> [ 2203.656681] RDX: 0000000000098b5e RSI: 0000000000000004 RDI:
> ffff88811a3c4f60
> [ 2203.656686] RBP: 0000000000000000 R08: 0000000000000001 R09:
> ffff88811a3c4f63
> [ 2203.656690] R10: ffffed10234789ec R11: 0000000000000001 R12:
> 0000000000000003
> [ 2203.656695] R13: ffff888100360000 R14: 0000000000000000 R15:
> 0000000000000000
> [ 2203.656703]  ? __cpuidle_text_start+0x8/0x8
> [ 2203.656713]  ? rcu_eqs_enter.constprop.0+0x81/0xa0
> [ 2203.656722]  ? __cpuidle_text_start+0x8/0x8
> [ 2203.656729]  default_idle_call+0x5a/0x150
> [ 2203.656735]  cpuidle_idle_call+0x1c6/0x220
> [ 2203.656742]  ? arch_cpu_idle_exit+0x40/0x40
> [ 2203.656748]  ? kvm_sched_clock_read+0xd/0x20
> [ 2203.656754]  ? sched_clock+0x5/0x10
> [ 2203.656760]  ? sched_clock_cpu+0x18/0x130
> [ 2203.656767]  ? kvm_clock_get_cycles+0xd/0x20
> [ 2203.656774]  ? tsc_verify_tsc_adjust+0x11f/0x160
> [ 2203.656780]  do_idle+0xab/0x100
> [ 2203.656786]  cpu_startup_entry+0x19/0x20
> [ 2203.656793]  secondary_startup_64_no_verify+0xc2/0xcb
> 
> [ 2203.657409] The buggy address belongs to the page:
> [ 2203.658648] page:0000000027a9842f refcount:1 mapcount:0
> mapping:0000000000000000 index:0x0 pfn:0x11a388
> [ 2203.658665] flags:
> 0x17ffffc0001000(reserved|node=0|zone=2|lastcpupid=0x1fffff)
> [ 2203.658675] raw: 0017ffffc0001000 ffffea000468e208 ffffea000468e208
> 0000000000000000
> [ 2203.658682] raw: 0000000000000000 0000000000000000 00000001ffffffff
> 0000000000000000
> [ 2203.658686] page dumped because: kasan: bad access detected
> ------------[ cut here ]-----------
> 
> To reproduce(ipvlan with IPVLAN_MODE_L3):
> Env setting:
> =======================================================
> modprobe ipvlan ipvlan_default_mode=1
> sysctl net.ipv4.conf.eth0.forwarding=1
> iptables -t nat -A POSTROUTING -s 20.0.0.0/255.255.255.0 -o eth0 -j
> MASQUERADE
> ip link add gw link eth0 type ipvlan
> ip -4 addr add 20.0.0.254/24 dev gw
> ip netns add net1
> ip link add ipv1 link eth0 type ipvlan
> ip link set ipv1 netns net1
> ip netns exec net1 ip link set ipv1 up
> ip netns exec net1 ip -4 addr add 20.0.0.4/24 dev ipv1
> ip netns exec net1 route add default gw 20.0.0.254
> ip netns exec net1 tc qdisc add dev ipv1 root netem loss 10%
> ifconfig gw up
> iptables -t filter -A OUTPUT -p tcp --dport 8888 -j REJECT --reject-with
> icmp-port-unreachable
> =======================================================
> And then excute the shell(curl any address of eth0 can reach):
> 
> for((i=1;i<=100000;i++))
> do
>         ip netns exec net1 curl x.x.x.x:8888
> done
> =======================================================
> 
> Signed-off-by: "t.feng" <fengtao40@...wei.com>
> Suggested-by: Florian Westphal <fw@...len.de>

Please include a suitable Fixes tag.

> ---
>  drivers/net/ipvlan/ipvlan_core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ipvlan/ipvlan_core.c b/drivers/net/ipvlan/ipvlan_core.c
> index 460b3d4f2245..9937d9f3df72 100644
> --- a/drivers/net/ipvlan/ipvlan_core.c
> +++ b/drivers/net/ipvlan/ipvlan_core.c
> @@ -436,6 +436,9 @@ static int ipvlan_process_v4_outbound(struct sk_buff *skb)
>  		goto err;
>  	}
>  	skb_dst_set(skb, &rt->dst);
> +
> +	memset(skb->cb, 0, sizeof(struct inet_skb_parm));

The preferred style to clear the inet cb is:

	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));


which generates exactly the same code, but is more grep friendly.

> +
>  	err = ip_local_out(net, skb->sk, skb);
>  	if (unlikely(net_xmit_eval(err)))
>  		dev->stats.tx_errors++;
> @@ -474,6 +477,9 @@ static int ipvlan_process_v6_outbound(struct sk_buff *skb)
>  		goto err;
>  	}
>  	skb_dst_set(skb, dst);
> +
> +	memset(skb->cb, 0, sizeof(struct inet6_skb_parm));

and here:

	memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

Cheers,

Paolo

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