[v6.1] INFO: rcu detected stall in sys_getsockopt (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 344a09659766 Linux 6.1.131
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=172d5004580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1eebf09bc04ebd78
dashboard link: https://syzkaller.appspot.com/bug?extid=19b96719a910448956cb
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bccba205a29a/disk-344a0965.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bdca79b3b5db/vmlinux-344a0965.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6c2271a91ef3/bzImage-344a0965.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+19b967...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P8008/3:b..l
(detected by 1, t=10502 jiffies, g=39317, q=27 ncpus=2)
task:syz.2.986 state:R running task stack:25848 pid:8008 ppid:4256 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5243 [inline]
__schedule+0x143f/0x4570 kernel/sched/core.c:6560
preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6872
irqentry_exit+0x53/0x80 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__sanitizer_cov_trace_switch+0x0/0xe0 kernel/kcov.c:326
Code: 39 c8 77 1e 49 ff c2 4c 89 12 48 c7 44 11 08 07 00 00 00 48 89 7c 11 10 48 89 74 11 18 4c 89 44 11 20 c3 0f 1f 80 00 00 00 00 <41> 57 41 56 41 54 53 48 8b 46 08 48 83 c0 f8 48 c1 c0 3d 48 83 f8
RSP: 0018:ffffc90006516ef0 EFLAGS: 00000297
RAX: 0000000000000002 RBX: ffff888076b98000 RCX: 0000000000080000
RDX: ffff88802f528000 RSI: ffffffff8e656dc0 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffff896cb0df R09: fffff52000ca2e07
R10: 0000000000000000 R11: dffffc0000000001 R12: ffffc90006517040
R13: ffffc90006517080 R14: dffffc0000000000 R15: 0000000000000001
ipv6_get_saddr_eval+0x66/0xe90 net/ipv6/addrconf.c:1558
__ipv6_dev_get_saddr+0x1d3/0x4a0 net/ipv6/addrconf.c:1712
ipv6_dev_get_saddr+0x417/0xbc0 net/ipv6/addrconf.c:1848
ip6_route_get_saddr include/net/ip6_route.h:152 [inline]
ip6_dst_lookup_tail+0xebc/0x1470 net/ipv6/ip6_output.c:1129
ip6_dst_lookup_flow+0xb5/0x170 net/ipv6/ip6_output.c:1255
sctp_v6_get_dst+0x955/0x1e80 net/sctp/ipv6.c:327
sctp_transport_route+0x10c/0x2b0 net/sctp/transport.c:455
sctp_packet_config+0x432/0xd90 net/sctp/output.c:103
sctp_outq_select_transport+0x470/0x580 net/sctp/outqueue.c:869
sctp_outq_flush_ctrl net/sctp/outqueue.c:903 [inline]
sctp_outq_flush+0x4ba/0x3d70 net/sctp/outqueue.c:1212
sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
sctp_do_sm+0x55e7/0x5c80 net/sctp/sm_sideeffect.c:1170
sctp_primitive_ASSOCIATE+0x91/0xc0 net/sctp/primitive.c:73
__sctp_connect+0x9b7/0xe10 net/sctp/socket.c:1232
__sctp_setsockopt_connectx net/sctp/socket.c:1334 [inline]
sctp_getsockopt_connectx3+0x467/0x720 net/sctp/socket.c:1419
sctp_getsockopt+0x3a0/0x7f0 net/sctp/socket.c:8125
__sys_getsockopt+0x2b2/0x5d0 net/socket.c:2332
__do_sys_getsockopt net/socket.c:2347 [inline]
__se_sys_getsockopt net/socket.c:2344 [inline]
__x64_sys_getsockopt+0xb1/0xc0 net/socket.c:2344
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1dea18d169
RSP: 002b:00007f1deaf64038 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007f1dea3a5fa0 RCX: 00007f1dea18d169
RDX: 000000000000006f RSI: 0000000000000084 RDI: 0000000000000004
RBP: 00007f1dea20e2a0 R08: 00002000000002c0 R09: 0000000000000000
R10: 0000200000000280 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f1dea3a5fa0 R15: 00007ffe891ba938
</TASK>
rcu: rcu_preempt kthread starved for 10548 jiffies! g39317 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R running task stack:26712 pid:16 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5243 [inline]
__schedule+0x143f/0x4570 kernel/sched/core.c:6560
schedule+0xbf/0x180 kernel/sched/core.c:6636
schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
kthread+0x28d/0x320 kernel/kthread.c:376
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 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:567


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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 535ec20c5027 Linux 6.1.135
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15138374580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c2afad13ffca3ea1
dashboard link: https://syzkaller.appspot.com/bug?extid=19b96719a910448956cb
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11d1a368580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11e9e270580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2c79bcda1589/disk-535ec20c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/179c841623d5/vmlinux-535ec20c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/669b3c281b37/Image-535ec20c.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+19b967...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:

rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P4299/1:b..l
(detected by 1, t=10502 jiffies, g=4969, q=276 ncpus=2)
task:syz-executor316 state:R running task stack:0 pid:4299 ppid:4292 flags:0x00000004
Call trace:
__switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0xdd4/0x1b2c kernel/sched/core.c:6561
preempt_schedule_irq+0x8c/0x1b8 kernel/sched/core.c:6873
arm64_preempt_schedule_irq+0x44/0x58 arch/arm64/kernel/entry-common.c:265
__el1_irq arch/arm64/kernel/entry-common.c:474 [inline]
el1_interrupt+0x3c/0x54 arch/arm64/kernel/entry-common.c:486
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:491
el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:581
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
lock_acquire+0x24c/0x644 kernel/locking/lockdep.c:5665
rcu_lock_acquire+0x40/0x4c include/linux/rcupdate.h:350
rcu_read_lock include/linux/rcupdate.h:791 [inline]
net_generic+0x28/0x240 include/net/netns/generic.h:45
xt_find_table_lock+0x4c/0x394 net/netfilter/x_tables.c:1237
xt_request_find_table_lock+0x38/0x114 net/netfilter/x_tables.c:1284
get_info net/ipv6/netfilter/ip6_tables.c:981 [inline]
do_ip6t_get_ctl+0x6d0/0x1314 net/ipv6/netfilter/ip6_tables.c:1670
nf_getsockopt+0x264/0x284 net/netfilter/nf_sockopt.c:116
ipv6_getsockopt+0x2bc/0x3e4 net/ipv6/ipv6_sockglue.c:1512
tcp_getsockopt+0xcc/0xe8 net/ipv4/tcp.c:4469
sock_common_getsockopt+0xa8/0xc4 net/core/sock.c:3655
__sys_getsockopt+0x1e0/0x480 net/socket.c:2332

__do_sys_getsockopt net/socket.c:2347 [inline]
__se_sys_getsockopt net/socket.c:2344 [inline]

__arm64_sys_getsockopt+0xb8/0xd4 net/socket.c:2344
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
rcu: rcu_preempt kthread starved for 10506 jiffies! g4969 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R running task stack:0 pid:16 ppid:2 flags:0x00000008
Call trace:
__switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0xdd4/0x1b2c kernel/sched/core.c:6561
schedule+0xc4/0x170 kernel/sched/core.c:6637
schedule_timeout+0x180/0x2c8 kernel/time/timer.c:1965
rcu_gp_fqs_loop+0x2a8/0x134c kernel/rcu/tree.c:1706
rcu_gp_kthread+0xc0/0x2f8 kernel/rcu/tree.c:1905
kthread+0x250/0x2d8 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:864

rcu: Stack dump where RCU GP kthread last ran:

Task dump for CPU 0:
task:syz-executor316 state:R running task stack:0 pid:4372 ppid:4296 flags:0x00000001
Call trace:
__switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
0xffff0000c9e6a61c


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