[v5.15] INFO: rcu detected stall in inet6_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 29e53a5b1c4f Linux 5.15.194
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=163d81e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=1f899f1dad4e4591f20f
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/fa58515734cb/disk-29e53a5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/725ddff41050/vmlinux-29e53a5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3ede79550267/bzImage-29e53a5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f899f...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (1 GPs behind) idle=e75/1/0x4000000000000002 softirq=141595/141596 fqs=5240
(detected by 1, t=10502 jiffies, g=222869, q=1411)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7282 Comm: syz.9.9740 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:check_preemption_disabled+0x3/0x110 lib/smp_processor_id.c:13
Code: c7 c7 80 d0 12 8a e8 2c 01 00 00 65 ff 0d e1 15 5a 76 5b c3 00 00 cc 48 c7 c7 60 a4 59 8a 48 c7 c6 a0 a4 59 8a eb 00 55 41 57 <41> 56 53 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 44 24 08 65
RSP: 0018:ffffc90000007828 EFLAGS: 00000002
RAX: 0000000000000000 RBX: 0000000000000000 RCX: e234f273e1212d00
RDX: 0000000000000100 RSI: ffffffff8a59a4a0 RDI: ffffffff8a59a460
RBP: ffffc90000007908 R08: dffffc0000000000 R09: fffffbfff1ad32b6
R10: fffffbfff1ad32b6 R11: 1ffffffff1ad32b5 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8880b9000000 R15: 0000000000000806
FS: 00007fd694fb16c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd694f6ef98 CR3: 000000007e295000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:331 [inline]
rcu_nmi_exit+0x30/0xf0 kernel/rcu/tree.c:753
rcu_irq_exit_irqson+0x8b/0x110 kernel/rcu/tree.c:841
trace_irq_enable_rcuidle+0x11e/0x180 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x84/0x480 kernel/rcu/tree_plugin.h:674
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 ad 13 9e 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc90000007a00 EFLAGS: 00000206
RAX: e234f273e1212d00 RBX: 1ffff92000000f44 RCX: e234f273e1212d00
RDX: dffffc0000000000 RSI: ffffffff8a0b1820 RDI: ffffffff8a59a4c0
RBP: ffffc90000007ae0 R08: dffffc0000000000 R09: fffffbfff1ff7a1a
R10: fffffbfff1ff7a1a R11: 1ffffffff1ff7a19 R12: ffffffff8c120b00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
rcu_read_unlock include/linux/rcupdate.h:771 [inline]
process_backlog+0x3e3/0x780 net/core/dev.c:6517
__napi_poll+0xc0/0x430 net/core/dev.c:7075
napi_poll net/core/dev.c:7142 [inline]
net_rx_action+0x4a8/0x9c0 net/core/dev.c:7232
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:should_resched arch/x86/include/asm/preempt.h:103 [inline]
RIP: 0010:__local_bh_enable_ip+0x132/0x1b0 kernel/softirq.c:408
Code: 8a e8 82 cc 60 08 65 66 8b 05 ca 25 bb 7e 66 85 c0 75 54 bf 01 00 00 00 e8 9b fe 08 00 e8 e6 74 35 00 fb 65 8b 05 76 fc b9 7e <85> c0 75 05 e8 25 07 b8 ff 48 c7 04 24 0e 36 e0 45 4b c7 04 37 00
RSP: 0018:ffffc90002f1f620 EFLAGS: 00000282
RAX: 0000000000000000 RBX: 0000000000000201 RCX: e234f273e1212d00
RDX: dffffc0000000000 RSI: ffffffff8a0b1820 RDI: ffffffff8a59a4c0
RBP: ffffc90002f1f6b8 R08: dffffc0000000000 R09: fffffbfff1ff7a1a
R10: fffffbfff1ff7a1a R11: 1ffffffff1ff7a19 R12: ffffffff889074c1
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff920005e3ec4
spin_unlock_bh include/linux/spinlock.h:408 [inline]
__ip6_del_rt+0xa1/0x150 net/ipv6/route.c:3889
ip6_del_rt+0xb0/0xf0 net/ipv6/route.c:3903
__ipv6_ifa_notify+0x81a/0xda0 net/ipv6/addrconf.c:6212
ipv6_ifa_notify net/ipv6/addrconf.c:6224 [inline]
ipv6_del_addr+0x63e/0x880 net/ipv6/addrconf.c:1324
inet6_addr_del+0x3ee/0x5a0 net/ipv6/addrconf.c:3060
addrconf_del_ifaddr+0x110/0x160 net/ipv6/addrconf.c:3111
inet6_ioctl+0x1d2/0x240 net/ipv6/af_inet6.c:590
sock_do_ioctl+0xd3/0x2f0 net/socket.c:1140
sock_ioctl+0x4ed/0x6e0 net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
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: 0033:0x7fd696d49ec9
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:00007fd694fb1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd696fa0fa0 RCX: 00007fd696d49ec9
RDX: 0000200000000000 RSI: 0000000000008936 RDI: 0000000000000006
RBP: 00007fd696dccf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd696fa1038 R14: 00007fd696fa0fa0 R15: 00007ffcc51d3538
</TASK>


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