[PATCH 5.4 61/80] net: sched: limit TC_ACT_REPEAT loops

From: Greg Kroah-Hartman
Date: Mon Feb 21 2022 - 04:13:15 EST

From: Eric Dumazet <edumazet@xxxxxxxxxx>

commit 5740d068909676d4bdb5c9c00c37a83df7728909 upstream.

We have been living dangerously, at the mercy of malicious users,
abusing TC_ACT_REPEAT, as shown by this syzpot report [1].

Add an arbitrary limit (32) to the number of times an action can
return TC_ACT_REPEAT.

v2: switch the limit to 32 instead of 10.
Use net_warn_ratelimited() instead of pr_err_once().

[1] (C repro available on demand)

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-...!: (10500 ticks this GP) idle=021/1/0x4000000000000000 softirq=5592/5592 fqs=0
(t=10502 jiffies g=5305 q=190)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10502 jiffies! g5305 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=0 timer-softirq=3527
rcu: rcu_preempt kthread starved for 10505 jiffies! g5305 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:I stack:29344 pid: 14 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:4986 [inline]
__schedule+0xab2/0x4db0 kernel/sched/core.c:6295
schedule+0xd2/0x260 kernel/sched/core.c:6368
schedule_timeout+0x14a/0x2a0 kernel/time/timer.c:1881
rcu_gp_fqs_loop+0x186/0x810 kernel/rcu/tree.c:1963
rcu_gp_kthread+0x1de/0x320 kernel/rcu/tree.c:2136
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3646 Comm: syz-executor358 Not tainted 5.17.0-rc3-syzkaller-00149-gbf8e59fd315f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:rep_nop arch/x86/include/asm/vdso/processor.h:13 [inline]
RIP: 0010:cpu_relax arch/x86/include/asm/vdso/processor.h:18 [inline]
RIP: 0010:pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:437 [inline]
RIP: 0010:__pv_queued_spin_lock_slowpath+0x3b8/0xb40 kernel/locking/qspinlock.c:508
Code: 48 89 eb c6 45 01 01 41 bc 00 80 00 00 48 c1 e9 03 83 e3 07 41 be 01 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8d 2c 01 eb 0c <f3> 90 41 83 ec 01 0f 84 72 04 00 00 41 0f b6 45 00 38 d8 7f 08 84
RSP: 0018:ffffc9000283f1b0 EFLAGS: 00000206
RAX: 0000000000000003 RBX: 0000000000000000 RCX: 1ffff1100fc0071e
RDX: 0000000000000001 RSI: 0000000000000201 RDI: 0000000000000000
RBP: ffff88807e0038f0 R08: 0000000000000001 R09: ffffffff8ffbf9ff
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000004c1e
R13: ffffed100fc0071e R14: 0000000000000001 R15: ffff8880b9c3aa80
FS: 00005555562bf300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffdbfef12b8 CR3: 00000000723c2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
do_raw_spin_lock+0x200/0x2b0 kernel/locking/spinlock_debug.c:115
spin_lock_bh include/linux/spinlock.h:354 [inline]
sch_tree_lock include/net/sch_generic.h:610 [inline]
sch_tree_lock include/net/sch_generic.h:605 [inline]
prio_tune+0x3b9/0xb50 net/sched/sch_prio.c:211
prio_init+0x5c/0x80 net/sched/sch_prio.c:244
qdisc_create.constprop.0+0x44a/0x10f0 net/sched/sch_api.c:1253
tc_modify_qdisc+0x4c5/0x1980 net/sched/sch_api.c:1660
rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5594
netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x539/0x7e0 net/netlink/af_netlink.c:1343
netlink_sendmsg+0x904/0xe00 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:705 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:725
____sys_sendmsg+0x6e8/0x810 net/socket.c:2413
___sys_sendmsg+0xf3/0x170 net/socket.c:2467
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2496
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f7ee98aae99
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdbfef12d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ffdbfef1300 RCX: 00007f7ee98aae99
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 000000000000000d R09: 000000000000000d
R10: 000000000000000d R11: 0000000000000246 R12: 00007ffdbfef12f0
R13: 00000000000f4240 R14: 000000000004ca47 R15: 00007ffdbfef12e4
</TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 2.293 msecs
NMI backtrace for cpu 1
CPU: 1 PID: 3260 Comm: kworker/1:3 Not tainted 5.17.0-rc3-syzkaller-00149-gbf8e59fd315f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: mld mld_ifc_work
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
rcu_dump_cpu_stacks+0x25e/0x3f0 kernel/rcu/tree_stall.h:343
print_cpu_stall kernel/rcu/tree_stall.h:604 [inline]
check_cpu_stall kernel/rcu/tree_stall.h:688 [inline]
rcu_pending kernel/rcu/tree.c:3919 [inline]
rcu_sched_clock_irq.cold+0x5c/0x759 kernel/rcu/tree.c:2617
update_process_times+0x16d/0x200 kernel/time/timer.c:1785
tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226
tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1428
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x1c0/0xe50 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x31c/0x790 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
__sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1103
sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1097
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0xc/0x70 kernel/kcov.c:286
Code: 00 00 00 48 89 7c 30 e8 48 89 4c 30 f0 4c 89 54 d8 20 48 89 10 5b c3 0f 1f 80 00 00 00 00 41 89 f8 bf 03 00 00 00 4c 8b 14 24 <89> f1 65 48 8b 34 25 00 70 02 00 e8 14 f9 ff ff 84 c0 74 4b 48 8b
RSP: 0018:ffffc90002c5eea8 EFLAGS: 00000246
RAX: 0000000000000007 RBX: ffff88801c625800 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: ffff8880137d3100 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff874fcd88 R11: 0000000000000000 R12: ffff88801d692dc0
R13: ffff8880137d3104 R14: 0000000000000000 R15: ffff88801d692de8
tcf_police_act+0x358/0x11d0 net/sched/act_police.c:256
tcf_action_exec net/sched/act_api.c:1049 [inline]
tcf_action_exec+0x1a6/0x530 net/sched/act_api.c:1026
tcf_exts_exec include/net/pkt_cls.h:326 [inline]
route4_classify+0xef0/0x1400 net/sched/cls_route.c:179
__tcf_classify net/sched/cls_api.c:1549 [inline]
tcf_classify+0x3e8/0x9d0 net/sched/cls_api.c:1615
prio_classify net/sched/sch_prio.c:42 [inline]
prio_enqueue+0x3a7/0x790 net/sched/sch_prio.c:75
dev_qdisc_enqueue+0x40/0x300 net/core/dev.c:3668
__dev_xmit_skb net/core/dev.c:3756 [inline]
__dev_queue_xmit+0x1f61/0x3660 net/core/dev.c:4081
neigh_hh_output include/net/neighbour.h:533 [inline]
neigh_output include/net/neighbour.h:547 [inline]
ip_finish_output2+0x14dc/0x2170 net/ipv4/ip_output.c:228
__ip_finish_output net/ipv4/ip_output.c:306 [inline]
__ip_finish_output+0x396/0x650 net/ipv4/ip_output.c:288
ip_finish_output+0x32/0x200 net/ipv4/ip_output.c:316
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip_output+0x196/0x310 net/ipv4/ip_output.c:430
dst_output include/net/dst.h:451 [inline]
ip_local_out+0xaf/0x1a0 net/ipv4/ip_output.c:126
iptunnel_xmit+0x628/0xa50 net/ipv4/ip_tunnel_core.c:82
geneve_xmit_skb drivers/net/geneve.c:966 [inline]
geneve_xmit+0x10c8/0x3530 drivers/net/geneve.c:1077
__netdev_start_xmit include/linux/netdevice.h:4683 [inline]
netdev_start_xmit include/linux/netdevice.h:4697 [inline]
xmit_one net/core/dev.c:3473 [inline]
dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3489
__dev_queue_xmit+0x2985/0x3660 net/core/dev.c:4116
neigh_hh_output include/net/neighbour.h:533 [inline]
neigh_output include/net/neighbour.h:547 [inline]
ip6_finish_output2+0xf7a/0x14f0 net/ipv6/ip6_output.c:126
__ip6_finish_output net/ipv6/ip6_output.c:191 [inline]
__ip6_finish_output+0x61e/0xe90 net/ipv6/ip6_output.c:170
ip6_finish_output+0x32/0x200 net/ipv6/ip6_output.c:201
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip6_output+0x1e4/0x530 net/ipv6/ip6_output.c:224
dst_output include/net/dst.h:451 [inline]
NF_HOOK include/linux/netfilter.h:307 [inline]
NF_HOOK include/linux/netfilter.h:301 [inline]
mld_sendpack+0x9a3/0xe40 net/ipv6/mcast.c:1826
mld_send_cr net/ipv6/mcast.c:2127 [inline]
mld_ifc_work+0x71c/0xdc0 net/ipv6/mcast.c:2659
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
----------------
Code disassembly (best guess):
0: 48 89 eb mov %rbp,%rbx
3: c6 45 01 01 movb $0x1,0x1(%rbp)
7: 41 bc 00 80 00 00 mov $0x8000,%r12d
d: 48 c1 e9 03 shr $0x3,%rcx
11: 83 e3 07 and $0x7,%ebx
14: 41 be 01 00 00 00 mov $0x1,%r14d
1a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
21: fc ff df
24: 4c 8d 2c 01 lea (%rcx,%rax,1),%r13
28: eb 0c jmp 0x36
* 2a: f3 90 pause <-- trapping instruction
2c: 41 83 ec 01 sub $0x1,%r12d
30: 0f 84 72 04 00 00 je 0x4a8
36: 41 0f b6 45 00 movzbl 0x0(%r13),%eax
3b: 38 d8 cmp %bl,%al
3d: 7f 08 jg 0x47
3f: 84 .byte 0x84

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Cc: Jiri Pirko <jiri@xxxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220215235305.3272331-1-eric.dumazet@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sched/act_api.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -652,15 +652,24 @@ int tcf_action_exec(struct sk_buff *skb,
restart_act_graph:
for (i = 0; i < nr_actions; i++) {
const struct tc_action *a = actions[i];
+ int repeat_ttl;

if (jmp_prgcnt > 0) {
jmp_prgcnt -= 1;
continue;
}
+
+ repeat_ttl = 32;
repeat:
ret = a->ops->act(skb, a, res);
- if (ret == TC_ACT_REPEAT)
- goto repeat; /* we need a ttl - JHS */
+
+ if (unlikely(ret == TC_ACT_REPEAT)) {
+ if (--repeat_ttl != 0)
+ goto repeat;
+ /* suspicious opcode, stop pipeline */
+ net_warn_ratelimited("TC_ACT_REPEAT abuse ?\n");
+ return TC_ACT_OK;
+ }

if (TC_ACT_EXT_CMP(ret, TC_ACT_JUMP)) {
jmp_prgcnt = ret & TCA_ACT_MAX_PRIO_MASK;