The processing method of tcp_mark_head_lost error reported by linux system
- 2021-07-01 08:36:26
- OfStack
Problem description
Recently, one host reported the following kernel information:
Jul 8 10:47:42 cztest kernel: ------------[ cut here ]------------
Jul 8 10:47:42 cztest kernel: WARNING: at net/ipv4/tcp_input.c:2269 tcp_mark_head_lost+0x113/0x290()
Jul 8 10:47:42 cztest kernel: Modules linked in: iptable_filter ip_tables binfmt_misc cdc_ether usbnet mii xt_multiport dm_mirror dm_region_hash dm_log dm_mod intel_powerclamp coretemp intel_rapl iosf_mbi kvm_intel kvm irqbypass crc32_p
clmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd ipmi_ssif ipmi_devintf ipmi_si mei_me pcspkr iTCO_wdt mxm_wmi iTCO_vendor_support dcdbas mei sg sb_edac edac_core ipmi_msghandler shpchp lpc_ich wmi acpi_p
ower_meter xfs libcrc32c sd_mod crc_t10dif crct10dif_generic mgag200 drm_kms_helper crct10dif_pclmul crct10dif_common syscopyarea crc32c_intel sysfillrect sysimgblt fb_sys_fops igb ttm ptp drm ahci pps_core libahci dca i2c_algo_bit libat
a megaraid_sas i2c_core fjes [last unloaded: ip_tables]
Jul 8 10:47:42 cztest kernel: CPU: 10 PID: 0 Comm: swapper/10 Tainted: G W ------------ 3.10.0-514.16.1.el7.x86_64 #1
Jul 8 10:47:42 cztest kernel: Hardware name: Dell Inc. PowerEdge R630/02C2CP, BIOS 2.3.4 11/08/2016
Jul 8 10:47:42 cztest kernel: 0000000000000000 dd79fe633eacd853 ffff88103e743880 ffffffff81686ac3
Jul 8 10:47:42 cztest kernel: ffff88103e7438b8 ffffffff81085cb0 ffff8806d5c57800 ffff88010a4e6c80
Jul 8 10:47:42 cztest kernel: 0000000000000001 00000000f90e778c 0000000000000001 ffff88103e7438c8
Jul 8 10:47:42 cztest kernel: Call Trace:
Jul 8 10:47:42 cztest kernel: <IRQ> [<ffffffff81686ac3>] dump_stack+0x19/0x1b
Jul 8 10:47:42 cztest kernel: [<ffffffff81085cb0>] warn_slowpath_common+0x70/0xb0
Jul 8 10:47:42 cztest kernel: [<ffffffff81085dfa>] warn_slowpath_null+0x1a/0x20
Jul 8 10:47:42 cztest kernel: [<ffffffff815c3663>] tcp_mark_head_lost+0x113/0x290
Jul 8 10:47:42 cztest kernel: [<ffffffff815c3f47>] tcp_update_scoreboard+0x67/0x80
Jul 8 10:47:42 cztest kernel: [<ffffffff815c964d>] tcp_fastretrans_alert+0x6dd/0xb50
Jul 8 10:47:42 cztest kernel: [<ffffffff815ca49d>] tcp_ack+0x8dd/0x12e0
Jul 8 10:47:42 cztest kernel: [<ffffffff815cb3a8>] tcp_rcv_established+0x118/0x760
Jul 8 10:47:42 cztest kernel: [<ffffffff815d5f8a>] tcp_v4_do_rcv+0x10a/0x340
Jul 8 10:47:42 cztest kernel: [<ffffffff812a84c6>] ? security_sock_rcv_skb+0x16/0x20
Jul 8 10:47:42 cztest kernel: [<ffffffff815d76d9>] tcp_v4_rcv+0x799/0x9a0
Jul 8 10:47:42 cztest kernel: [<ffffffffa0140036>] ? iptable_filter_hook+0x36/0x80 [iptable_filter]
Jul 8 10:47:42 cztest kernel: [<ffffffff815b1094>] ip_local_deliver_finish+0xb4/0x1f0
Jul 8 10:47:42 cztest kernel: [<ffffffff815b1379>] ip_local_deliver+0x59/0xd0
Jul 8 10:47:42 cztest kernel: [<ffffffff815b0fe0>] ? ip_rcv_finish+0x350/0x350
Jul 8 10:47:42 cztest kernel: [<ffffffff815b0d1a>] ip_rcv_finish+0x8a/0x350
Jul 8 10:47:42 cztest kernel: [<ffffffff815b16a6>] ip_rcv+0x2b6/0x410
Jul 8 10:47:42 cztest kernel: [<ffffffff815700d2>] __netif_receive_skb_core+0x582/0x800
Jul 8 10:47:42 cztest kernel: [<ffffffff815dc694>] ? tcp4_gro_receive+0x134/0x1b0
Jul 8 10:47:42 cztest kernel: [<ffffffff811dc861>] ? __slab_free+0x81/0x2f0
Jul 8 10:47:42 cztest kernel: [<ffffffff81570368>] __netif_receive_skb+0x18/0x60
Jul 8 10:47:42 cztest kernel: [<ffffffff815703f0>] netif_receive_skb_internal+0x40/0xc0
Jul 8 10:47:42 cztest kernel: [<ffffffff81571578>] napi_gro_receive+0xd8/0x130
Jul 8 10:47:42 cztest kernel: [<ffffffffa018b237>] igb_clean_rx_irq+0x387/0x700 [igb]
Jul 8 10:47:42 cztest kernel: [<ffffffff8155e862>] ? skb_release_data+0xf2/0x140
Jul 8 10:47:42 cztest kernel: [<ffffffffa018b933>] igb_poll+0x383/0x770 [igb]
Jul 8 10:47:42 cztest kernel: [<ffffffff815d3120>] ? tcp_write_timer_handler+0x200/0x200
Jul 8 10:47:42 cztest kernel: [<ffffffff81570c00>] net_rx_action+0x170/0x380
Jul 8 10:47:42 cztest kernel: [<ffffffff8108f63f>] __do_softirq+0xef/0x280
Jul 8 10:47:42 cztest kernel: [<ffffffff81698c1c>] call_softirq+0x1c/0x30
Jul 8 10:47:42 cztest kernel: [<ffffffff8102d365>] do_softirq+0x65/0xa0
Jul 8 10:47:42 cztest kernel: [<ffffffff8108f9d5>] irq_exit+0x115/0x120
Jul 8 10:47:42 cztest kernel: [<ffffffff816997b8>] do_IRQ+0x58/0xf0
Jul 8 10:47:42 cztest kernel: [<ffffffff8168e86d>] common_interrupt+0x6d/0x6d
Jul 8 10:47:42 cztest kernel: <EOI> [<ffffffff81514a22>] ? cpuidle_enter_state+0x52/0xc0
Jul 8 10:47:42 cztest kernel: [<ffffffff81514b69>] cpuidle_idle_call+0xd9/0x210
Jul 8 10:47:42 cztest kernel: [<ffffffff810350ee>] arch_cpu_idle+0xe/0x30
Jul 8 10:47:42 cztest kernel: [<ffffffff810e82a5>] cpu_startup_entry+0x245/0x290
Jul 8 10:47:42 cztest kernel: [<ffffffff8104f07a>] start_secondary+0x1ba/0x230
Jul 8 10:47:42 cztest kernel: ---[ end trace 6bc65b0c591c1794 ]---The host environment is as follows:
System | Dell Inc.; PowerEdge R620;
Platform | Linux
Kernel | Centos 3.10.0-514.16.1.el7.x86_64
Total Memory | 64G
Treatment instructions
The stack printing process is similar to xfs alarm processing, The general process is that after the kernel turns on sack and fack functions, the fast retransmission and selective retransmission required in the network transmission process will be processed by tcp_mark_head_lost function of tcp_input. c file, which mainly marks the number of messages lost in the transmission process. As shown below, the kernel stack information reported by the system is triggered by tcp_verify_left_out function call in tcp_mark_head_lost function:
// source/include/net/tcp.h
#define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
{
return tp->sacked_out + tp->lost_out;
}
// source/include/asm-generic/bug.h
#define __WARN() warn_slowpath_null(__FILE__, __LINE__)
#ifndef WARN_ON
#define WARN_ON(condition) ({ \
__WARN(); \
})
#endif
// source/net/ipv4/tcp_input.c
/* Detect loss in event "A" above by marking head of queue up as lost.
* For FACK or non-SACK(Reno) senders, the first "packets" number of segments
* are considered lost. For RFC3517 SACK, a segment is considered lost if it
* has at least tp->reordering SACKed seqments above it; "packets" refers to
* the maximum SACKed segments to pass before reaching this limit.
*/
static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
{
struct tcp_sock *tp = tcp_sk(sk);
....
tcp_verify_left_out(tp); // trigger dump_stack
}
...
static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
{
struct tcp_sock *tp = tcp_sk(sk);
if (tcp_is_reno(tp)) {
tcp_mark_head_lost(sk, 1, 1);
} else if (tcp_is_fack(tp)) {
int lost = tp->fackets_out - tp->reordering;
if (lost <= 0)
lost = 1;
tcp_mark_head_lost(sk, lost, 0);
} else {
int sacked_upto = tp->sacked_out - tp->reordering;
if (sacked_upto >= 0)
tcp_mark_head_lost(sk, sacked_upto, 0);
else if (fast_rexmit)
tcp_mark_head_lost(sk, 1, 1);
}
}As described in redhat-536483, this error message 1 is generally caused by tcp bug and may be triggered when the kernel uses the released tcp socket buffer linked list:
Root Cause
A use after free issue related to the TCP kernel socket buffer linked list. Thus it is a bug in the TCP kernel code. Although the bug is in TCP kernel code, but it could get triggered in multiple ways. It could get triggered due to NFS, or due to even an application(say java process).
Treatment mode
Upgrade kernel
As shown below, redhat may have fixed use after free related bug for tcp_* related functions in version 3.10. 0-520, and you can try to upgrade to deal with this problem:
centos 7.x changelog
* Thu Nov 03 2016 Rafael Aquini <aquini@redhat.com> [3.10.0-520.el7]
- [net] tcp: fix use after free in tcp_xmit_retransmit_queue() (Mateusz Guzik) [1379531] {CVE-2016-6828}
Turn off fack/sack functionality
According to the documents of Red Hat Knowledge Base, the tcp_mark_head_lost function is mainly used to mark the number of messages lost in the process of fast retransmission and selection confirmation, so it may be possible to temporarily close the fack/sack parameter to avoid this problem:
sysctl -w net.ipv4.tcp_fack=0
sysctl -w net.ipv4.tcp_sack=0You can try the second method first, and consider upgrading the kernel version if you still have problems.
Reference
redhat-536483
bug-1367091
cve-2016-6828
kernel-commit
Summarize