Message-ID: <68147631.050a0220.53db9.0006.GAE@google.com>
Date: Fri, 02 May 2025 00:37:21 -0700
From: syzbot <syzbot+7d36dbfae4115f887499@...kaller.appspotmail.com>
To: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] BUG: soft lockup in sctp_generate_timeout_event

Hello,

syzbot found the following issue on:

HEAD commit:    b4432656b36e Linux 6.15-rc4
git tree:       bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=13fee39b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a9a25b7a36123454
dashboard link: https://syzkaller.appspot.com/bug?extid=7d36dbfae4115f887499
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c9ea4f1822ea/disk-b4432656.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c5effc66ca81/vmlinux-b4432656.xz
kernel image: https://storage.googleapis.com/syzbot-assets/49364ea611a8/bzImage-b4432656.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7d36dbfae4115f887499@...kaller.appspotmail.com

watchdog: BUG: soft lockup - CPU#1 stuck for 123s! [syz.0.827:8572]
Modules linked in:
irq event stamp: 19239949
hardirqs last  enabled at (19239948): [<ffffffff8b55e3c4>] irqentry_exit+0x74/0x90 kernel/entry/common.c:357
hardirqs last disabled at (19239949): [<ffffffff8b55cdbe>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1049
softirqs last  enabled at (2908914): [<ffffffff8185c3fa>] __do_softirq kernel/softirq.c:613 [inline]
softirqs last  enabled at (2908914): [<ffffffff8185c3fa>] invoke_softirq kernel/softirq.c:453 [inline]
softirqs last  enabled at (2908914): [<ffffffff8185c3fa>] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
softirqs last disabled at (2908917): [<ffffffff8185c3fa>] __do_softirq kernel/softirq.c:613 [inline]
softirqs last disabled at (2908917): [<ffffffff8185c3fa>] invoke_softirq kernel/softirq.c:453 [inline]
softirqs last disabled at (2908917): [<ffffffff8185c3fa>] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
CPU: 1 UID: 0 PID: 8572 Comm: syz.0.827 Not tainted 6.15.0-rc4-syzkaller-gb4432656b36e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:842 [inline]
RIP: 0010:ip6_pol_route+0x19e/0x1180 net/ipv6/route.c:2264
Code: c0 45 31 c9 41 57 e8 f1 d2 90 f7 48 83 c4 08 e8 78 a5 48 01 41 89 c6 31 ff 89 c6 e8 2c 8a b2 f7 45 85 f6 74 10 e8 12 ad 99 f7 <84> c0 74 0e e8 d9 85 b2 f7 eb 58 e8 d2 85 b2 f7 eb 51 e8 4b a5 48
RSP: 0018:ffffc90000a07ce0 EFLAGS: 00000202
RAX: 0000000000000001 RBX: 0000000000000002 RCX: 9f9af6a53f4fb200
RDX: ffff888025f61e00 RSI: ffffffff8bc1cdc0 RDI: ffffffff8bc1cd80
RBP: ffffc90000a07e00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8a0d38b2 R12: ffffc90000a08380
R13: 0000000000000000 R14: 0000000000000001 R15: ffffffff8a0d38b2
FS:  00007f576e13d6c0(0000) GS:ffff8881261cc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000309e2000 CR4: 00000000003526f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 pol_lookup_func include/net/ip6_fib.h:616 [inline]
 __fib6_rule_action net/ipv6/fib6_rules.c:237 [inline]
 fib6_rule_action+0x206/0x7d0 net/ipv6/fib6_rules.c:275
 fib_rules_lookup+0x767/0xe90 net/core/fib_rules.c:339
 fib6_rule_lookup+0x18e/0x6f0 net/ipv6/fib6_rules.c:112
 ip6_route_output_flags_noref net/ipv6/route.c:2674 [inline]
 ip6_route_output_flags+0x364/0x5d0 net/ipv6/route.c:2686
 ip6_dst_lookup_tail+0x299/0x1500 net/ipv6/ip6_output.c:1156
 ip6_dst_lookup_flow+0x47/0xe0 net/ipv6/ip6_output.c:1259
 sctp_v6_get_dst+0xffa/0x1bc0 net/sctp/ipv6.c:384
 sctp_transport_route+0x115/0x2f0 net/sctp/transport.c:457
 sctp_packet_config+0x478/0xd90 net/sctp/output.c:103
 sctp_packet_singleton+0x158/0x330 net/sctp/outqueue.c:777
 sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline]
 sctp_outq_flush+0x4f0/0x3140 net/sctp/outqueue.c:1212
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
 sctp_do_sm+0x5332/0x5a20 net/sctp/sm_sideeffect.c:1169
 sctp_generate_timeout_event+0x22e/0x360 net/sctp/sm_sideeffect.c:295
 call_timer_fn+0x17b/0x5f0 kernel/time/timer.c:1789
 expire_timers kernel/time/timer.c:1840 [inline]
 __run_timers kernel/time/timer.c:2414 [inline]
 __run_timer_base+0x61a/0x860 kernel/time/timer.c:2426
 run_timer_base kernel/time/timer.c:2435 [inline]
 run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2445
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:preempt_schedule_irq+0xb0/0x150 kernel/sched/core.c:7090
Code: 24 20 f6 44 24 21 02 74 0c 90 0f 0b 48 f7 03 08 00 00 00 74 64 bf 01 00 00 00 e8 eb c3 39 f6 e8 86 43 70 f6 fb bf 01 00 00 00 <e8> 4b ab ff ff 48 c7 44 24 40 00 00 00 00 9c 8f 44 24 40 8b 44 24
RSP: 0018:ffffc90003777800 EFLAGS: 00000286
RAX: 9f9af6a53f4fb200 RBX: 0000000000000000 RCX: 9f9af6a53f4fb200
RDX: 0000000000000000 RSI: ffffffff8d749f78 RDI: 0000000000000001
RBP: ffffc900037778b0 R08: ffffffff8f7ed377 R09: 1ffffffff1efda6e
R10: dffffc0000000000 R11: fffffbfff1efda6f R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff920006eef00
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:354
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:lock_is_held_type+0x137/0x190 kernel/locking/lockdep.c:5943
Code: 01 75 44 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 4c 41 f7 c4 00 02 00 00 74 01 fb 65 48 8b 05 89 64 1f 07 <48> 3b 44 24 08 75 43 89 d8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc90003777978 EFLAGS: 00000206
RAX: 9f9af6a53f4fb200 RBX: 0000000000000000 RCX: 9f9af6a53f4fb200
RDX: 0000000000000000 RSI: ffffffff8d9350da RDI: ffffffff8bc1cde0
RBP: 00000000ffffffff R08: ffffc90003777c5f R09: 0000000000000000
R10: ffffc90003777c30 R11: fffff520006eef8c R12: 0000000000000246
R13: ffff888025f61e00 R14: ffffffff8df3b8c0 R15: 0000000000000000
 lock_is_held include/linux/lockdep.h:249 [inline]
 __might_resched+0xa6/0x610 kernel/sched/core.c:8780
 __might_fault+0x77/0x130 mm/memory.c:7149
 __copy_from_user include/linux/uaccess.h:106 [inline]
 check_xstate_in_sigframe arch/x86/kernel/fpu/signal.c:33 [inline]
 __fpu_restore_sig arch/x86/kernel/fpu/signal.c:344 [inline]
 fpu__restore_sig+0x1a4/0x10a0 arch/x86/kernel/fpu/signal.c:489
 restore_sigcontext arch/x86/kernel/signal_64.c:95 [inline]
 __ia32_sys_rt_sigreturn+0x661/0x7b0 arch/x86/kernel/signal_64.c:266
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f576d38e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f576e13d0e8 EFLAGS: 00000246
RAX: fffffffffffffffc RBX: 00007f576d5b5fa8 RCX: 00007f576d38e969
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f576d5b5fa8
RBP: 00007f576d5b5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f576d5b5fac
R13: 0000000000000000 R14: 00007ffeaf203f10 R15: 00007ffeaf203ff8
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 2912 Comm: kworker/u8:8 Not tainted 6.15.0-rc4-syzkaller-gb4432656b36e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:340 [inline]
RIP: 0010:smp_call_function_many_cond+0xe69/0x11c0 kernel/smp.c:885
Code: 00 45 8b 2f 44 89 ee 83 e6 01 31 ff e8 20 6d 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 cb 68 0b 00 eb 37 f3 90 <43> 0f b6 04 2c 84 c0 75 10 41 f7 07 01 00 00 00 74 1e e8 b0 68 0b
RSP: 0018:ffffc9000bc8f700 EFLAGS: 00000293
RAX: ffffffff81b45620 RBX: ffff8880b883ad40 RCX: ffff88802f0d9e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000bc8f860 R08: ffffffff8f7ed377 R09: 1ffffffff1efda6e
R10: dffffc0000000000 R11: fffffbfff1efda6f R12: 1ffff11017127e99
R13: dffffc0000000000 R14: 0000000000000001 R15: ffff8880b893f4c8
FS:  0000000000000000(0000) GS:ffff8881260cc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffffa814fb0 CR3: 000000000dd36000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1052
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2455 [inline]
 text_poke_bp_batch+0x319/0x940 arch/x86/kernel/alternative.c:2665
 text_poke_flush arch/x86/kernel/alternative.c:2856 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2863
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x128/0x250 kernel/jump_label.c:210
 static_key_enable+0x1a/0x20 kernel/jump_label.c:223
 toggle_allocation_gate+0xad/0x240 mm/kfence/core.c:850
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xadb/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
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