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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>
 		2025-05-01 18:04:08 -07:00
..
6lowpan
…
9p 9p: Use hashtable.h for hash_errmap 2025-03-23 06:20:48 +09:00
802 net: 802: Remove unused p8022 code 2025-04-22 07:04:02 -07:00
8021q net: 802: Remove unused p8022 code 2025-04-22 07:04:02 -07:00
appletalk treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
atm treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
ax25 treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
batman-adv batman-adv: Fix double-hold of meshif when getting enabled 2025-04-15 17:56:47 -07:00
bluetooth Bluetooth: L2CAP: copy RX timestamp to new fragments 2025-04-25 15:03:19 -04:00
bpf
…
bridge net: bridge: mcast: update multicast contex when vlan state is changed 2025-04-23 13:02:20 +01:00
caif
…
can can: fix missing decrement of j1939_proto.inuse_idx 2025-04-15 12:18:07 +02:00
ceph A small CephFS encryption-related fix and a dead code cleanup. 2025-04-25 15:51:28 -07:00
core xsk: convert xdp_copy_frags_from_zc() to use page_pool_dev_alloc() 2025-04-29 14:26:26 -07:00
dcb
…
devlink devlink: add value check to devlink_info_version_put() 2025-04-15 07:36:31 -07:00
dns_resolver
…
dsa net: dsa: avoid refcount warnings when ds->ops->tag_8021q_vlan_del() fails 2025-04-16 18:14:44 -07:00
ethernet
…
ethtool net: ethtool: mm: reset verification status when link is down 2025-04-18 08:43:10 -07:00
handshake
…
hsr net: hsr: sync hw addr of slave2 according to slave1 hw addr on PRP 2025-04-14 12:40:06 +01:00
ieee802154 inet: frags: save a pair of atomic operations in reassembly 2025-03-18 13:18:36 +01:00
ife
…
ipv4 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-05-01 15:11:38 -07:00
ipv6 ipv6: sr: switch to GFP_ATOMIC flag to allocate memory during seg6local LWT setup 2025-05-01 18:04:08 -07:00
iucv s390: Convert MACHINE_IS_[LPAR|VM|KVM], etc, machine_is_[lpar|vm|kvm]() 2025-03-04 17:18:07 +01:00
kcm
…
key
…
l2tp net: move misc netdev_lock flavors to a separate header 2025-03-08 09:06:50 -08:00
l3mdev net: fib_rules: Fix iif / oif matching on L3 master device 2025-04-15 17:54:56 -07:00
lapb treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
llc treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
mac80211 wifi: mac80211: restore monitor for outgoing frames 2025-04-23 14:44:22 +02:00
mac802154
…
mctp net: mctp: Set SOCK_RCU_FREE 2025-04-11 18:42:34 -07:00
mpls mpls: Use nlmsg_payload in mpls_valid_getroute_req 2025-04-15 08:28:54 -07:00
mptcp Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-04-24 11:20:52 -07:00
ncsi net: ncsi: Fix GCPS 64-bit member variables 2025-04-15 15:19:55 +02:00
netfilter netfilter: nf_tables: export set count and backend name to userspace 2025-04-29 00:00:27 +02:00
netlabel
…
netlink
…
netrom treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
nfc treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
nsh
…
openvswitch net: openvswitch: fix nested key length validation in the set() action 2025-04-14 16:15:38 -07:00
packet treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
phonet
…
psample
…
qrtr
…
rds
…
rfkill
…
rose treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
rxrpc rxrpc: rxgk: Fix some reference count leaks 2025-04-24 18:06:05 -07:00
sched Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-05-01 15:11:38 -07:00
sctp Including fixes from netfilter. 2025-04-10 08:52:18 -07:00
shaper
…
smc smc: Fix lockdep false-positive for IPPROTO_SMC. 2025-04-11 14:14:26 -07:00
strparser
…
sunrpc nfsd-6.15 fixes: 2025-04-26 10:43:03 -07:00
switchdev net: switchdev: Convert blocking notification chain to a raw one 2025-03-11 11:30:28 +01:00
tipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-04-24 11:20:52 -07:00
tls net: tls: explicitly disallow disconnect 2025-04-08 11:38:49 +02:00
unix af_unix: Remove unix_unhash() 2025-04-10 17:32:57 -07:00
vmw_vsock vsock: avoid timeout during connect() if the socket is closing 2025-04-02 17:19:30 -07:00
wireless treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
x25 treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
xdp Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-05-01 15:11:38 -07:00
xfrm xfrm: Convert xfrmi_exit_batch_rtnl() to ->exit_rtnl(). 2025-04-14 17:08:43 -07:00
Kconfig net: Retire DCCP socket. 2025-04-11 18:58:10 -07:00
Kconfig.debug
…
Makefile net: Retire DCCP socket. 2025-04-11 18:58:10 -07:00
compat.c
…
devres.c
…
socket.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-03-26 09:32:10 -07:00
sysctl_net.c
…