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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9eec9a14ee10 Linux 5.15.198
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17f1153a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=bcc1f729417d8ee6a1e9
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6bf27c1311e7/disk-9eec9a14.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/20b573bab166/vmlinux-9eec9a14.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f5ff7bd08305/bzImage-9eec9a14.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bcc1f7...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (1 GPs behind) idle=e69/1/0x4000000000000000 softirq=75943/75944 fqs=5248
(detected by 1, t=10502 jiffies, g=104401, q=1569)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 25983 Comm: syz.8.4523 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:perf_trace_buf_alloc+0xfa/0x300 kernel/trace/trace_event_perf.c:419
Code: e8 cb 25 f8 ff 49 bd 00 00 00 00 00 fc ff df 4d 8d bf 20 51 03 00 4e 8d 24 e5 20 08 e3 8b 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 <74> 08 4c 89 e7 e8 bc 29 3d 00 4d 03 3c 24 4c 89 f0 48 c1 e8 03 42
RSP: 0018:ffffc90000007900 EFLAGS: 00000046
RAX: 1ffffffff17c6104 RBX: 0000000000000014 RCX: ffff88805dcbbb80
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000001 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffffff8be30820
R13: dffffc0000000000 R14: ffffc90000007980 R15: 00000000000351c8
FS: 00007f8dc723c6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000000 CR3: 0000000060db6000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
perf_trace_preemptirq_template+0x180/0x360 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0x108/0x180 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+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 c2 ef 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007b00 EFLAGS: 00000206
RAX: 027a40e62eae5500 RBX: 1ffff92000000f64 RCX: 027a40e62eae5500
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f780
RBP: ffffc90000007bd8 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffffff8c322f00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
rcu_read_unlock include/linux/rcupdate.h:772 [inline]
ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4eb/0xb70 kernel/time/hrtimer.c:1749
hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
handle_softirqs+0x339/0x830 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x13b/0x230 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:__fdget+0x0/0x210 fs/file.c:1023
Code: e8 b5 c6 ed ff e9 c8 fc ff ff 44 89 f9 80 e1 07 80 c1 03 38 c1 7c c0 4c 89 ff e8 0b c7 ed ff eb b6 66 0f 1f 84 00 00 00 00 00 <55> 41 57 41 56 41 55 41 54 53 50 89 fb 49 bc 00 00 00 00 00 fc ff
RSP: 0018:ffffc900030afee0 EFLAGS: 00000283
RAX: ffffffff81cd6228 RBX: ffffc900030aff20 RCX: 0000000000080000
RDX: ffffc9000faef000 RSI: 00000000000000b5 RDI: 00000000ffffffff
RBP: ffffc900030aff48 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: 00000000400454ca
R13: ffffffffffffffff R14: ffffc900030aff58 R15: 0000200000000080
fdget include/linux/file.h:66 [inline]
__do_sys_ioctl fs/ioctl.c:862 [inline]
__se_sys_ioctl+0x20/0x170 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: 0033:0x7f8dc8fe0eb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8dc723c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8dc925bfa0 RCX: 00007f8dc8fe0eb9
RDX: 0000200000000080 RSI: 00000000400454ca RDI: ffffffffffffffff
RBP: 00007f8dc904ec1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8dc925c038 R14: 00007f8dc925bfa0 R15: 00007ffca4164c78
</TASK>


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