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linux/net/ipv6
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Andrea Mayer 14a0087e72 ipv6: sr: switch to GFP_ATOMIC flag to allocate memory during seg6local LWT setup 
Recent updates to the locking mechanism that protects IPv6 routing tables
[1] have affected the SRv6 networking subsystem. Such changes cause
problems with some SRv6 Endpoints behaviors, like End.B6.Encaps and also
impact SRv6 counters.

Starting from commit 169fd62799 ("ipv6: Get rid of RTNL for SIOCADDRT and
RTM_NEWROUTE."), the inet6_rtm_newroute() function no longer needs to
acquire the RTNL lock for creating and configuring IPv6 routes and set up
lwtunnels.
The RTNL lock can be avoided because the ip6_route_add() function
finishes setting up a new route in a section protected by RCU.
This makes sure that no dev/nexthops can disappear during the operation.
Because of this, the steps for setting up lwtunnels - i.e., calling
lwtunnel_build_state() - are now done in a RCU lock section and not
under the RTNL lock anymore.

However, creating and configuring a lwtunnel instance in an
RCU-protected section can be problematic when that tunnel needs to
allocate memory using the GFP_KERNEL flag.
For example, the following trace shows what happens when an SRv6
End.B6.Encaps behavior is instantiated after commit 169fd62799 ("ipv6:
Get rid of RTNL for SIOCADDRT and RTM_NEWROUTE."):

[ 3061.219696] BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
[ 3061.226136] in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 445, name: ip
[ 3061.232101] preempt_count: 0, expected: 0
[ 3061.235414] RCU nest depth: 1, expected: 0
[ 3061.238622] 1 lock held by ip/445:
[ 3061.241458]  #0: ffffffff83ec64a0 (rcu_read_lock){....}-{1:3}, at: ip6_route_add+0x41/0x1e0
[ 3061.248520] CPU: 1 UID: 0 PID: 445 Comm: ip Not tainted 6.15.0-rc3-micro-vm-dev-00590-ge527e891492d #2058 PREEMPT(full)
[ 3061.248532] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 3061.248549] Call Trace:
[ 3061.248620]  <TASK>
[ 3061.248633]  dump_stack_lvl+0xa9/0xc0
[ 3061.248846]  __might_resched+0x218/0x360
[ 3061.248871]  __kmalloc_node_track_caller_noprof+0x332/0x4e0
[ 3061.248889]  ? rcu_is_watching+0x3a/0x70
[ 3061.248902]  ? parse_nla_srh+0x56/0xa0
[ 3061.248938]  kmemdup_noprof+0x1c/0x40
[ 3061.248952]  parse_nla_srh+0x56/0xa0
[ 3061.248969]  seg6_local_build_state+0x2e0/0x580
[ 3061.248992]  ? __lock_acquire+0xaff/0x1cd0
[ 3061.249013]  ? do_raw_spin_lock+0x111/0x1d0
[ 3061.249027]  ? __pfx_seg6_local_build_state+0x10/0x10
[ 3061.249068]  ? lwtunnel_build_state+0xe1/0x3a0
[ 3061.249274]  lwtunnel_build_state+0x10d/0x3a0
[ 3061.249303]  fib_nh_common_init+0xce/0x1e0
[ 3061.249337]  ? __pfx_fib_nh_common_init+0x10/0x10
[ 3061.249352]  ? in6_dev_get+0xaf/0x1f0
[ 3061.249369]  ? __rcu_read_unlock+0x64/0x2e0
[ 3061.249392]  fib6_nh_init+0x290/0xc30
[ 3061.249422]  ? __pfx_fib6_nh_init+0x10/0x10
[ 3061.249447]  ? __lock_acquire+0xaff/0x1cd0
[ 3061.249459]  ? _raw_spin_unlock_irqrestore+0x22/0x70
[ 3061.249624]  ? ip6_route_info_create+0x423/0x520
[ 3061.249641]  ? rcu_is_watching+0x3a/0x70
[ 3061.249683]  ip6_route_info_create_nh+0x190/0x390
[ 3061.249715]  ip6_route_add+0x71/0x1e0
[ 3061.249730]  ? __pfx_inet6_rtm_newroute+0x10/0x10
[ 3061.249743]  inet6_rtm_newroute+0x426/0xc50
[ 3061.249764]  ? avc_has_perm_noaudit+0x13d/0x360
[ 3061.249853]  ? __pfx_inet6_rtm_newroute+0x10/0x10
[ 3061.249905]  ? __lock_acquire+0xaff/0x1cd0
[ 3061.249962]  ? rtnetlink_rcv_msg+0x52f/0x890
[ 3061.249996]  ? __pfx_inet6_rtm_newroute+0x10/0x10
[ 3061.250012]  rtnetlink_rcv_msg+0x551/0x890
[ 3061.250040]  ? __pfx_rtnetlink_rcv_msg+0x10/0x10
[ 3061.250065]  ? __lock_acquire+0xaff/0x1cd0
[ 3061.250092]  netlink_rcv_skb+0xbd/0x1f0
[ 3061.250108]  ? __pfx_rtnetlink_rcv_msg+0x10/0x10
[ 3061.250124]  ? __pfx_netlink_rcv_skb+0x10/0x10
[ 3061.250179]  ? netlink_deliver_tap+0x10b/0x700
[ 3061.250210]  netlink_unicast+0x2e7/0x410
[ 3061.250232]  ? __pfx_netlink_unicast+0x10/0x10
[ 3061.250241]  ? __lock_acquire+0xaff/0x1cd0
[ 3061.250280]  netlink_sendmsg+0x366/0x670
[ 3061.250306]  ? __pfx_netlink_sendmsg+0x10/0x10
[ 3061.250313]  ? find_held_lock+0x2d/0xa0
[ 3061.250344]  ? import_ubuf+0xbc/0xf0
[ 3061.250370]  ? __pfx_netlink_sendmsg+0x10/0x10
[ 3061.250381]  __sock_sendmsg+0x13e/0x150
[ 3061.250420]  ____sys_sendmsg+0x33d/0x450
[ 3061.250442]  ? __pfx_____sys_sendmsg+0x10/0x10
[ 3061.250453]  ? __pfx_copy_msghdr_from_user+0x10/0x10
[ 3061.250489]  ? __pfx_slab_free_after_rcu_debug+0x10/0x10
[ 3061.250514]  ___sys_sendmsg+0xe5/0x160
[ 3061.250530]  ? __pfx____sys_sendmsg+0x10/0x10
[ 3061.250568]  ? __lock_acquire+0xaff/0x1cd0
[ 3061.250617]  ? find_held_lock+0x2d/0xa0
[ 3061.250678]  ? __virt_addr_valid+0x199/0x340
[ 3061.250704]  ? preempt_count_sub+0xf/0xc0
[ 3061.250736]  __sys_sendmsg+0xca/0x140
[ 3061.250750]  ? __pfx___sys_sendmsg+0x10/0x10
[ 3061.250786]  ? syscall_exit_to_user_mode+0xa2/0x1e0
[ 3061.250825]  do_syscall_64+0x62/0x140
[ 3061.250844]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 3061.250855] RIP: 0033:0x7f0b042ef914
[ 3061.250868] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b5 0f 1f 80 00 00 00 00 48 8d 05 e9 5d 0c 00 8b 00 85 c0 75 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 41 89 d4 55 48 89 f5 53
[ 3061.250876] RSP: 002b:00007ffc2d113ef8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[ 3061.250885] RAX: ffffffffffffffda RBX: 00000000680f93fa RCX: 00007f0b042ef914
[ 3061.250891] RDX: 0000000000000000 RSI: 00007ffc2d113f60 RDI: 0000000000000003
[ 3061.250897] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000008
[ 3061.250902] R10: fffffffffffff26d R11: 0000000000000246 R12: 0000000000000001
[ 3061.250907] R13: 000055a961f8a520 R14: 000055a961f63eae R15: 00007ffc2d115270
[ 3061.250952]  </TASK>

To solve this issue, we replace the GFP_KERNEL flag with the GFP_ATOMIC
one in those SRv6 Endpoints that need to allocate memory during the
setup phase. This change makes sure that memory allocations are handled
in a way that works with RCU critical sections.

[1] - https://lore.kernel.org/all/20250418000443.43734-1-kuniyu@amazon.com/

Fixes: 169fd62799 ("ipv6: Get rid of RTNL for SIOCADDRT and RTM_NEWROUTE.")
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250429132453.31605-1-andrea.mayer@uniroma2.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
History 2025-05-01 18:04:08 -07:00
..
ila net: ipv6: fix missing dst ref drop in ila lwtunnel 2025-03-06 11:08:45 +01:00
netfilter netfilter pull request 25-03-23 2025-03-25 08:29:13 -07:00
addrconf.c ipv6: Use nlmsg_payload in addrconf file 2025-04-16 18:33:02 -07:00
addrconf_core.c ipv6: Ensure natural alignment of const ipv6 loopback and router addresses 2024-01-30 12:43:18 +01:00
addrlabel.c ipv6: Use nlmsg_payload in addrlabel file 2025-04-16 18:33:02 -07:00
af_inet6.c ovpn: implement TCP transport 2025-04-17 12:30:03 +02:00
ah6.c net: fill in MODULE_DESCRIPTION()s for ipv6 modules 2024-02-09 14:12:01 -08:00
anycast.c netlink: add IPv6 anycast join/leave notifications 2025-01-09 12:54:45 +01:00
calipso.c netlabel: Fix NULL pointer exception caused by CALIPSO on IPv4 sockets 2025-04-02 16:01:04 -07:00
datagram.c ipv6: annotate data-races around np->ucast_oif 2023-12-11 10:59:17 +00:00
esp6.c ipsec-2025-01-27 2025-01-27 15:15:12 -08:00
esp6_offload.c xfrm: Add an inbound percpu state cache. 2024-10-29 11:56:18 +01:00
exthdrs.c net: use sock_kmemdup for ip_options 2025-03-03 17:16:34 -08:00
exthdrs_core.c ipv6: Fix out-of-bounds access in ipv6_find_tlv() 2023-05-24 08:43:39 +01:00
exthdrs_offload.c net: gso: add HBH extension header offload support 2024-01-05 08:11:49 -08:00
fib6_notifier.c net: do not acquire rtnl in fib_seq_sum() 2024-10-11 15:35:05 -07:00
fib6_rules.c ipv6: fib_rules: Add DSCP mask matching 2025-02-21 16:08:48 -08:00
fou6.c net: Add MODULE_DESCRIPTION entries to network modules 2020-06-20 21:33:57 -07:00
icmp.c inet: ping: avoid skb_clone() dance in ping_rcv() 2025-02-28 14:41:33 -08:00
inet6_connection_sock.c net: Unexport shared functions for DCCP. 2025-04-11 18:58:11 -07:00
inet6_hashtables.c inet: call inet6_ehashfn() once from inet6_hash_connect() 2025-03-06 15:26:02 -08:00
ioam6.c net: convert to nla_get_*_default() 2024-11-11 10:32:06 -08:00
ioam6_iptunnel.c net: ipv6: ioam6: fix double reallocation 2025-04-17 12:52:34 +02:00
ip6_checksum.c net: udp: fix handling of CHECKSUM_COMPLETE packets 2018-10-24 14:18:16 -07:00
ip6_fib.c ipv6: Protect nh->f6i_list with spinlock and flag. 2025-04-24 09:29:56 +02:00
ip6_flowlabel.c treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
ip6_gre.c ipv6: Convert tunnel devices' ->exit_batch_rtnl() to ->exit_rtnl(). 2025-04-14 17:08:42 -07:00
ip6_icmp.c net: icmp: pass zeroed opts from icmp{,v6}_ndo_send before sending 2021-02-23 11:29:52 -08:00
ip6_input.c ipv6: Use RCU in ip6_input() 2025-02-06 16:14:15 -08:00
ip6_offload.c net: gro: initialize network_offset in network layer 2024-05-27 16:46:59 -07:00
ip6_offload.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
ip6_output.c net: Retire DCCP socket. 2025-04-11 18:58:10 -07:00
ip6_tunnel.c ipv6: Convert tunnel devices' ->exit_batch_rtnl() to ->exit_rtnl(). 2025-04-14 17:08:42 -07:00
ip6_udp_tunnel.c net: fill in MODULE_DESCRIPTION()s for ipv6 modules 2024-02-09 14:12:01 -08:00
ip6_vti.c ipv6: Convert tunnel devices' ->exit_batch_rtnl() to ->exit_rtnl(). 2025-04-14 17:08:42 -07:00
ip6mr.c treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
ipcomp6.c xfrm: ipcomp: add extack to ipcomp{4,6}_init_state 2022-09-29 07:18:00 +02:00
ipv6_sockglue.c ipv6: avoid indirect calls for SOL_IP socket options 2024-08-26 14:53:50 -07:00
Kconfig net: ipv6: select DST_CACHE from IPV6_RPL_LWTUNNEL 2024-09-22 19:52:07 +01:00
Makefile net/tcp: Introduce TCP_AO setsockopt()s 2023-10-27 10:35:44 +01:00
mcast.c ipv6: mcast: add RCU protection to mld_newpack() 2025-02-13 08:37:21 -08:00
mcast_snoop.c net: bridge: mcast: fix broken length + header check for MRDv6 Adv. 2021-04-27 14:02:06 -07:00
mip6.c net: fill in MODULE_DESCRIPTION()s for ipv6 modules 2024-02-09 14:12:01 -08:00
ndisc.c ndisc: ndisc_send_redirect() cleanup 2025-02-15 09:08:46 -08:00
netfilter.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2024-06-13 13:13:46 -07:00
output_core.c ipv6: annotate data-races around cnf.hop_limit 2024-03-01 08:42:31 +00:00
ping.c ipv6: initialize inet socket cookies with sockcm_init 2025-02-18 18:27:20 -08:00
proc.c minmax: add a few more MIN_T/MAX_T users 2024-07-28 13:41:14 -07:00
protocol.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
raw.c ipv6: initialize inet socket cookies with sockcm_init 2025-02-18 18:27:20 -08:00
reassembly.c inet: frags: save a pair of atomic operations in reassembly 2025-03-18 13:18:36 +01:00
route.c ip: load balance tcp connections to single dst addr and port 2025-04-29 16:22:25 +02:00
rpl.c ipv6: rpl: Remove pskb(_may)?_pull() in ipv6_rpl_srh_rcv(). 2023-06-19 11:32:58 -07:00
rpl_iptunnel.c net: ipv6: fix dst ref loop on input in rpl lwt 2025-02-27 14:18:22 +01:00
seg6.c ipv6: sr: restruct ifdefines 2024-05-30 18:29:38 -07:00
seg6_hmac.c ipv6: sr: fix memleak in seg6_hmac_init_algo 2024-05-21 13:16:25 +02:00
seg6_iptunnel.c net: ipv6: fix dst ref loop on input in seg6 lwt 2025-02-27 14:18:21 +01:00
seg6_local.c ipv6: sr: switch to GFP_ATOMIC flag to allocate memory during seg6local LWT setup 2025-05-01 18:04:08 -07:00
sit.c ipv6: Convert tunnel devices' ->exit_batch_rtnl() to ->exit_rtnl(). 2025-04-14 17:08:42 -07:00
syncookies.c tcp: use sk_skb_reason_drop to free rx packets 2024-06-19 12:44:22 +01:00
sysctl_net_ipv6.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
tcp_ao.c net/tcp: Wire up l3index to TCP-AO 2023-10-27 10:35:46 +01:00
tcp_ipv6.c ip: load balance tcp connections to single dst addr and port 2025-04-29 16:22:25 +02:00
tcpv6_offload.c net: use sock_gen_put() when sk_state is TCP_TIME_WAIT 2025-05-01 07:00:19 -07:00
tunnel6.c net: fill in MODULE_DESCRIPTION()s for ipv6 modules 2024-02-09 14:12:01 -08:00
udp.c udp_tunnel: create a fastpath GRO lookup. 2025-04-08 18:19:41 -07:00
udp_impl.h tcp/udp: Call inet6_destroy_sock() in IPv6 sk->sk_destruct(). 2022-10-12 17:50:37 -07:00
udp_offload.c udp_tunnel: create a fastpath GRO lookup. 2025-04-08 18:19:41 -07:00
udplite.c udplite: remove UDPLITE_BIT 2023-09-14 16:16:36 +02:00
xfrm6_input.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2024-05-09 10:01:01 -07:00
xfrm6_output.c xfrm: Fix the usage of skb->sk 2025-01-20 07:06:53 +01:00
xfrm6_policy.c xfrm: respect ip protocols rules criteria when performing dst lookups 2024-09-23 07:02:07 +02:00
xfrm6_protocol.c xfrm: add support for UDPv6 encapsulation of ESP 2020-04-28 11:28:36 +02:00
xfrm6_state.c xfrm: remove output_finish indirection from xfrm_state_afinfo 2020-05-06 09:40:08 +02:00
xfrm6_tunnel.c ipsec-next-2024-03-06 2024-03-08 10:56:05 +00:00