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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 91d48252ad4b Linux 5.15.202
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17102a02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=0132fdde24ca3953b1e1
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/1f63ca11335d/disk-91d48252.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/85d7c8824423/vmlinux-91d48252.xz
kernel image: https://storage.googleapis.com/syzbot-assets/11897ccd5b62/bzImage-91d48252.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0132fd...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (1 GPs behind) idle=84b/1/0x4000000000000000 softirq=39978/39979 fqs=2096
(detected by 1, t=10506 jiffies, g=57433, q=1835)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 15926 Comm: syz.7.2657 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:asm_sysvec_irq_work+0x0/0x20 arch/x86/include/asm/idtentry.h:707
Code: e9 a5 03 00 00 90 90 90 90 90 0f 01 ca fc 6a ff e8 a5 02 00 00 48 89 c4 48 89 e7 e8 7a 3c dc ff e9 85 03 00 00 90 90 90 90 90 <0f> 01 ca fc 6a ff e8 85 02 00 00 48 89 c4 48 89 e7 e8 4a 41 dc ff
RSP: 0018:ffffc90000007ad8 EFLAGS: 00000006
RAX: 7f605ec65d1e5e00 RBX: 1ffff92000000f64 RCX: 7f605ec65d1e5e00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f980
RBP: ffffc90000007bd8 R08: ffffffff901d40c7 R09: 1ffffffff203a818
R10: dffffc0000000000 R11: fffffbfff203a819 R12: ffffffff8c322f00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
FS: 00007f759a6696c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f759a227000 CR3: 0000000077aab000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
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 12 f2 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
__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+0x4f2/0xb70 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:account_kernel_stack+0x22c/0x390 kernel/fork.c:387
Code: 85 e4 75 1c e8 65 97 31 00 48 83 fb 38 75 1d eb 29 e8 58 97 31 00 e8 13 df 74 08 4d 85 e4 74 e4 e8 49 97 31 00 fb 48 83 fb 38 <74> 0e e8 3d 97 31 00 48 83 c3 08 e9 ad fe ff ff e8 2f 97 31 00 e9
RSP: 0018:ffffc9000152edc0 EFLAGS: 00000293
RAX: ffffffff814789c7 RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc90010890000 RSI: 000000000007674c RDI: 000000000007674d
RBP: ffffc9000152eec8 R08: ffffffff901d40c7 R09: 1ffffffff203a818
R10: dffffc0000000000 R11: fffffbfff203a819 R12: 0000000000000200
R13: 1ffff920002a5dbc R14: ffff88806001e7a0 R15: 0000000000000000
release_task_stack kernel/fork.c:432 [inline]
put_task_stack+0x8f/0x140 kernel/fork.c:444
finish_task_switch+0x26f/0x640 kernel/sched/core.c:4961
context_switch kernel/sched/core.c:5052 [inline]
__schedule+0x11f7/0x43c0 kernel/sched/core.c:6395
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6571
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6596
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
put_obj_stock mm/memcontrol.c:2179 [inline]
refill_obj_stock+0x3a0/0x470 mm/memcontrol.c:3256
memcg_slab_free_hook+0x157/0x1f0 mm/slab.h:364
do_slab_free mm/slub.c:3437 [inline]
___cache_free+0x63/0x120 mm/slub.c:3511
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xd0 mm/kasan/common.c:444
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:728 [inline]
__kernfs_new_node+0xe3/0x6c0 fs/kernfs/dir.c:593
kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:669
__kernfs_create_file+0x47/0x2e0 fs/kernfs/file.c:985
cgroup_add_file kernel/cgroup/cgroup.c:4090 [inline]
cgroup_addrm_files+0xac5/0x1020 kernel/cgroup/cgroup.c:4152
css_populate_dir+0x19b/0x2f0 kernel/cgroup/cgroup.c:1739
cgroup_mkdir+0xca0/0xec0 kernel/cgroup/cgroup.c:5604
kernfs_iop_mkdir+0x24c/0x3d0 fs/kernfs/dir.c:1175
vfs_mkdir+0x387/0x570 fs/namei.c:4073
do_mkdirat+0x1df/0x5b0 fs/namei.c:4098
__do_sys_mkdir fs/namei.c:4118 [inline]
__se_sys_mkdir fs/namei.c:4116 [inline]
__x64_sys_mkdir+0x6a/0x80 fs/namei.c:4116
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: 0033:0x7f759c430799
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:00007f759a669028 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007f759c6aa090 RCX: 00007f759c430799
RDX: 0000000000000000 RSI: 000000000000000c RDI: 0000200000000000
RBP: 00007f759c4c6bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f759c6aa128 R14: 00007f759c6aa090 R15: 00007ffd4fe2dbe8
</TASK>


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