[v5.15] INFO: rcu detected stall in tcp_write_timer (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 43bb85222e53 Linux 5.15.193
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12752ae2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=17b5e26c2a6a7eedcb8c
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0bc183664ae8/disk-43bb8522.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0fc2f6618934/vmlinux-43bb8522.xz
kernel image: https://storage.googleapis.com/syzbot-assets/af70b3957f4c/bzImage-43bb8522.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+17b5e2...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (1 GPs behind) idle=c3d/1/0x4000000000000000 softirq=63936/63942 fqs=4564
(t=10500 jiffies g=84397 q=2208)
NMI backtrace for cpu 0
CPU: 0 PID: 20131 Comm: syz.0.4500 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<IRQ>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
rcu_dump_cpu_stacks+0x22f/0x380 kernel/rcu/tree_stall.h:349
print_cpu_stall+0x31d/0x5f0 kernel/rcu/tree_stall.h:633
check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
rcu_pending kernel/rcu/tree.c:3936 [inline]
rcu_sched_clock_irq+0x6d8/0x1110 kernel/rcu/tree.c:2619
update_process_times+0x193/0x200 kernel/time/timer.c:1818
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1690 [inline]
__hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1754
hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1816
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:seqcount_lockdep_reader_access+0x17b/0x1c0 include/linux/seqlock.h:106
Code: 00 4d 85 e4 75 16 e8 54 cc 0f 00 eb 15 e8 4d cc 0f 00 e8 88 ef 40 08 4d 85 e4 74 ea e8 3e cc 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 66 43 c7 44 3e 09 00 00 43 c6 44 3e 0b 00
RSP: 0018:ffffc90000006ce0 EFLAGS: 00000246
RAX: ffffffff8167fee2 RBX: 0000000000000000 RCX: ffff88807ab95940
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000006d80 R08: dffffc0000000000 R09: fffffbfff1ff7832
R10: fffffbfff1ff7832 R11: 1ffffffff1ff7831 R12: 0000000000000200
R13: 000001fb63109b96 R14: 1ffff92000000d9c R15: dffffc0000000000
ktime_get_with_offset+0x90/0x320 kernel/time/timekeeping.c:872
ktime_get_real include/linux/timekeeping.h:79 [inline]
__net_timestamp include/linux/skbuff.h:3970 [inline]
net_timestamp_set net/core/dev.c:2195 [inline]
dev_queue_xmit_nit+0x83c/0xb00 net/core/dev.c:2345
xmit_one net/core/dev.c:3644 [inline]
dev_hard_start_xmit+0x13e/0x7e0 net/core/dev.c:3665
sch_direct_xmit+0x24e/0x4a0 net/sched/sch_generic.c:342
__dev_xmit_skb net/core/dev.c:3884 [inline]
__dev_queue_xmit+0x170e/0x2ed0 net/core/dev.c:4253
NF_HOOK+0x2d4/0x360 include/linux/netfilter.h:302
arp_xmit+0x142/0x230 net/ipv4/arp.c:642
arp_solicit+0xc1b/0xe60 net/ipv4/arp.c:391
neigh_probe net/core/neighbour.c:1017 [inline]
__neigh_event_send+0xf12/0x14e0 net/core/neighbour.c:1178
neigh_event_send include/net/neighbour.h:438 [inline]
neigh_resolve_output+0x1b3/0x6a0 net/core/neighbour.c:1488
neigh_output include/net/neighbour.h:509 [inline]
ip_finish_output2+0xca1/0x1080 net/ipv4/ip_output.c:228
dst_output include/net/dst.h:452 [inline]
ip_local_out net/ipv4/ip_output.c:126 [inline]
__ip_queue_xmit+0x11c3/0x1c00 net/ipv4/ip_output.c:532
__tcp_transmit_skb+0x1ced/0x31c0 net/ipv4/tcp_output.c:1404
tcp_transmit_skb net/ipv4/tcp_output.c:1422 [inline]
__tcp_retransmit_skb+0x92c/0x1290 net/ipv4/tcp_output.c:3267
tcp_retransmit_skb+0x2e/0x350 net/ipv4/tcp_output.c:3290
tcp_retransmit_timer+0x144b/0x2540 net/ipv4/tcp_timer.c:570
tcp_write_timer_handler+0x205/0x9a0 net/ipv4/tcp_timer.c:655
tcp_write_timer+0x126/0x280 net/ipv4/tcp_timer.c:675
call_timer_fn+0x16c/0x530 kernel/time/timer.c:1451
expire_timers kernel/time/timer.c:1496 [inline]
__run_timers+0x525/0x7c0 kernel/time/timer.c:1767
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780
handle_softirqs+0x328/0x820 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x12f/0x220 kernel/softirq.c:659
irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:on_stack arch/x86/include/asm/stacktrace.h:60 [inline]
RIP: 0010:stack_access_ok arch/x86/kernel/unwind_orc.c:347 [inline]
RIP: 0010:deref_stack_reg+0x8c/0x120 arch/x86/kernel/unwind_orc.c:357
Code: 85 92 00 00 00 41 83 3f 00 0f 95 c0 4d 39 f5 0f 96 c1 20 c1 4c 39 f5 0f 97 c0 20 c8 3c 01 75 14 49 8d 46 08 4c 39 e8 0f 97 c1 <48> 39 e8 0f 96 c0 84 c1 75 32 49 8d 7f 28 48 89 f8 48 c1 e8 03 42
RSP: 0018:ffffc9000331f870 EFLAGS: 00000202
RAX: ffffc9000331fea8 RBX: ffffc9000331f9a8 RCX: 0000000000000001
RDX: ffffc9000331f9a8 RSI: ffffc9000331fea0 RDI: ffffc9000331f978
RBP: ffffc90003320000 R08: dffffc0000000000 R09: ffffc9000331f9b8
R10: fffff52000663f39 R11: 1ffff92000663f37 R12: dffffc0000000000
R13: ffffc90003318000 R14: ffffc9000331fea0 R15: ffffc9000331f968
unwind_next_frame+0x115d/0x1d90 arch/x86/kernel/unwind_orc.c:-1
arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
__kasan_slab_alloc+0x9c/0xd0 mm/kasan/common.c:467
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
slab_alloc mm/slub.c:3233 [inline]
kmem_cache_alloc+0x100/0x290 mm/slub.c:3238
kmem_cache_zalloc include/linux/slab.h:725 [inline]
lsm_inode_alloc security/security.c:595 [inline]
security_inode_alloc+0x30/0x110 security/security.c:1033
inode_init_always+0x8f4/0xcb0 fs/inode.c:232
alloc_inode fs/inode.c:268 [inline]
new_inode_pseudo+0x8e/0x210 fs/inode.c:1001
sock_alloc net/socket.c:626 [inline]
__sock_create+0x129/0x900 net/socket.c:1450
sock_create net/socket.c:1542 [inline]
__sys_socket+0xe2/0x170 net/socket.c:1584
__do_sys_socket net/socket.c:1593 [inline]
__se_sys_socket net/socket.c:1591 [inline]
__x64_sys_socket+0x76/0x80 net/socket.c:1591
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fc1fea76ec9
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:00007fc1fccbd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
RAX: ffffffffffffffda RBX: 00007fc1fecce090 RCX: 00007fc1fea76ec9
RDX: 0000000000000073 RSI: 0000000000000002 RDI: 000000000000000a
RBP: 00007fc1feaf9f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc1fecce128 R14: 00007fc1fecce090 R15: 00007ffe0d11caa8
</TASK>


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