netdev - Re: [syzbot] [net?] INFO: task hung in del_device

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Message-ID: <689c348c.050a0220.7f033.0141.GAE@google.com>
Date: Tue, 12 Aug 2025 23:45:32 -0700
From: syzbot <syzbot+6d10ecc8a97cc10639f9@...kaller.appspotmail.com>
To: andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	hdanton@...a.com, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] INFO: task hung in del_device_store

syzbot has found a reproducer for the following issue on:

HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=15704da2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
dashboard link: https://syzkaller.appspot.com/bug?extid=6d10ecc8a97cc10639f9
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12702af0580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15816842580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6d10ecc8a97cc10639f9@...kaller.appspotmail.com

INFO: task syz-executor:6692 blocked for more than 144 seconds.
      Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:0     pid:6692  tgid:6692  ppid:1      task_flags:0x400140 flags:0x00000001
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:741 (T)
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x13b0/0x2864 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:7058
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7115
 __mutex_lock_common+0xca0/0x24ac kernel/locking/mutex.c:676
 __mutex_lock kernel/locking/mutex.c:760 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812
 del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
 bus_attr_store+0x80/0xa4 drivers/base/bus.c:172
 sysfs_kf_write+0x1a8/0x23c fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x314/0x488 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x540/0xa3c fs/read_write.c:686
 ksys_write+0x120/0x210 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:746
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
INFO: task syz-executor:6698 blocked for more than 144 seconds.
      Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:0     pid:6698  tgid:6698  ppid:6696   task_flags:0x400140 flags:0x00800000
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:741 (T)
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x13b0/0x2864 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:7058
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7115
 __mutex_lock_common+0xca0/0x24ac kernel/locking/mutex.c:676
 __mutex_lock kernel/locking/mutex.c:760 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812
 device_lock include/linux/device.h:911 [inline]
 device_del+0xa4/0x808 drivers/base/core.c:3840
 device_unregister+0x2c/0xcc drivers/base/core.c:3919
 nsim_bus_dev_del drivers/net/netdevsim/bus.c:483 [inline]
 del_device_store+0x27c/0x31c drivers/net/netdevsim/bus.c:244
 bus_attr_store+0x80/0xa4 drivers/base/bus.c:172
 sysfs_kf_write+0x1a8/0x23c fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x314/0x488 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x540/0xa3c fs/read_write.c:686
 ksys_write+0x120/0x210 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:746
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
INFO: task syz-executor:6701 blocked for more than 144 seconds.
      Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:0     pid:6701  tgid:6701  ppid:6699   task_flags:0x400140 flags:0x00800000
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:741 (T)
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x13b0/0x2864 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:7058
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7115
 __mutex_lock_common+0xca0/0x24ac kernel/locking/mutex.c:676
 __mutex_lock kernel/locking/mutex.c:760 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812
 del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
 bus_attr_store+0x80/0xa4 drivers/base/bus.c:172
 sysfs_kf_write+0x1a8/0x23c fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x314/0x488 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x540/0xa3c fs/read_write.c:686
 ksys_write+0x120/0x210 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:746
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
INFO: task syz-executor:6706 blocked for more than 144 seconds.
      Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:0     pid:6706  tgid:6706  ppid:6705   task_flags:0x400140 flags:0x00800000
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:741 (T)
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x13b0/0x2864 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:7058
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7115
 __mutex_lock_common+0xca0/0x24ac kernel/locking/mutex.c:676
 __mutex_lock kernel/locking/mutex.c:760 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812
 del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
 bus_attr_store+0x80/0xa4 drivers/base/bus.c:172
 sysfs_kf_write+0x1a8/0x23c fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x314/0x488 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x540/0xa3c fs/read_write.c:686
 ksys_write+0x120/0x210 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:746
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Showing all locks held in the system:
1 lock held by khungtaskd/32:
 #0: ffff80008f9a9060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire+0x4/0x48 include/linux/rcupdate.h:330
3 locks held by kworker/u8:2/41:
3 locks held by pr/ttyAMA-1/43:
2 locks held by kworker/u8:5/1987:
7 locks held by kworker/u8:7/2184:
5 locks held by kworker/u8:8/2656:
5 locks held by kworker/u8:9/4759:
1 lock held by klogd/6155:
3 locks held by udevd/6166:
1 lock held by dhcpcd/6220:
3 locks held by dhcpcd/6221:
2 locks held by getty/6308:
 #0: ffff0000d73b90a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff80009bbbb2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x34c/0xfa4 drivers/tty/n_tty.c:2222
4 locks held by syz-executor/6692:
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3107 [inline]
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: vfs_write+0x24c/0xa3c fs/read_write.c:682
 #1: ffff0000dc4fb888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1b4/0x488 fs/kernfs/file.c:325
 #2: ffff0000c6c77e18 (kn->active#55){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1d0/0x488 fs/kernfs/file.c:326
 #3: ffff800091a98908 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
5 locks held by kworker/0:4/6694:
5 locks held by syz-executor/6698:
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3107 [inline]
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: vfs_write+0x24c/0xa3c fs/read_write.c:682
 #1: ffff0000d9789088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1b4/0x488 fs/kernfs/file.c:325
 #2: ffff0000c6c77e18 (kn->active#55){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1d0/0x488 fs/kernfs/file.c:326
 #3: ffff800091a98908 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
 #4: ffff0000de8af0e8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #4: ffff0000de8af0e8 (&dev->mutex){....}-{4:4}, at: device_del+0xa4/0x808 drivers/base/core.c:3840
4 locks held by syz-executor/6701:
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3107 [inline]
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: vfs_write+0x24c/0xa3c fs/read_write.c:682
 #1: ffff0000c6553088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1b4/0x488 fs/kernfs/file.c:325
 #2: ffff0000c6c77e18 (kn->active#55){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1d0/0x488 fs/kernfs/file.c:326
 #3: ffff800091a98908 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
4 locks held by syz-executor/6706:
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3107 [inline]
 #0: ffff0000d802a428 (sb_writers#6){.+.+}-{0:0}, at: vfs_write+0x24c/0xa3c fs/read_write.c:682
 #1: ffff0000d7a2c488 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1b4/0x488 fs/kernfs/file.c:325
 #2: ffff0000c6c77e18 (kn->active#55){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1d0/0x488 fs/kernfs/file.c:326
 #3: ffff800091a98908 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd4/0x31c drivers/net/netdevsim/bus.c:234
3 locks held by syz-executor/6770:
3 locks held by kworker/u8:12/6772:
2 locks held by syz-executor/6776:

=============================================



---
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