linux-kernel - [syzbot] [mm?] INFO: rcu detected stall in hub

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Message-ID: <68a68107.050a0220.1f0557.0000.GAE@google.com>
Date: Wed, 20 Aug 2025 19:14:31 -0700
From: syzbot <syzbot+039eab266c6321a174bd@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, pasha.tatashin@...een.com, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [mm?] INFO: rcu detected stall in hub_event (2)

Hello,

syzbot found the following issue on:

HEAD commit:    90d970cade8e Merge tag 'ata-ata-6.17-rc2' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1193b3a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c5d01e11121d45
dashboard link: https://syzkaller.appspot.com/bug?extid=039eab266c6321a174bd
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/104fc9d3de89/disk-90d970ca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/59eb5344d41f/vmlinux-90d970ca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e0bed540b10c/bzImage-90d970ca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+039eab266c6321a174bd@...kaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P9643/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=87629, q=1145 ncpus=2)
task:kworker/1:13    state:R  running task     stack:22384 pid:9643  tgid:9643  ppid:2      task_flags:0x4288060 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7288
 irqentry_exit+0x36/0x90 kernel/entry/common.c:197
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:check_kcov_mode kernel/kcov.c:185 [inline]
RIP: 0010:write_comp_data+0x3c/0x90 kernel/kcov.c:246
Code: 8b 05 58 b3 1a 12 a9 00 01 ff 00 74 1d f6 c4 01 74 67 a9 00 00 0f 00 75 60 a9 00 00 f0 00 75 59 8b 82 3c 16 00 00 85 c0 74 4f <8b> 82 18 16 00 00 83 f8 03 75 44 48 8b 82 20 16 00 00 8b 92 1c 16
RSP: 0000:ffffc90004fdf430 EFLAGS: 00000246
RAX: 0000000080000000 RBX: 0000000000000004 RCX: ffffffff822dbf07
RDX: ffff88802883a440 RSI: 0000000000000004 RDI: 0000000000000006
RBP: 0000000000000003 R08: 0000000000000006 R09: 0000000000000004
R10: 0000000000000003 R11: 00000000000082fe R12: ffff8880200096f0
R13: ffff8880200096ec R14: 0000000000000002 R15: dffffc0000000000
 __page_table_check_zero+0x207/0x5d0 mm/page_table_check.c:139
 page_table_check_free include/linux/page_table_check.h:43 [inline]
 free_pages_prepare mm/page_alloc.c:1396 [inline]
 __free_frozen_pages+0x7b7/0x10f0 mm/page_alloc.c:2895
 discard_slab mm/slub.c:2753 [inline]
 __put_partials+0x165/0x1c0 mm/slub.c:3218
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:340
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4180 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_node_noprof+0x1d5/0x3b0 mm/slub.c:4281
 __alloc_skb+0x2b2/0x380 net/core/skbuff.c:659
 alloc_skb include/linux/skbuff.h:1336 [inline]
 alloc_uevent_skb+0x7d/0x210 lib/kobject_uevent.c:289
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline]
 kobject_uevent_env+0xca4/0x1870 lib/kobject_uevent.c:608
 device_del+0x623/0x9f0 drivers/base/core.c:3896
 usb_disable_device+0x355/0x7d0 drivers/usb/core/message.c:1418
 usb_disconnect+0x2e1/0x9c0 drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1c81/0x4fe0 drivers/usb/core/hub.c:5952
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3236
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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