6.6-stable review patch. If anyone has any objections, please let me know.
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From: Frederic Weisbecker frederic@kernel.org
commit 214e01ad4ed7158cab66498810094fac5d09b218 upstream.
Calling into kthread unparking unconditionally is mostly harmless when the kthread is already unparked. The wake up is then simply ignored because the target is not in TASK_PARKED state.
However if the kthread is per CPU, the wake up is preceded by a call to kthread_bind() which expects the task to be inactive and in TASK_PARKED state, which obviously isn't the case if it is unparked.
As a result, calling kthread_stop() on an unparked per-cpu kthread triggers such a warning:
WARNING: CPU: 0 PID: 11 at kernel/kthread.c:525 __kthread_bind_mask kernel/kthread.c:525 <TASK> kthread_stop+0x17a/0x630 kernel/kthread.c:707 destroy_workqueue+0x136/0xc40 kernel/workqueue.c:5810 wg_destruct+0x1e2/0x2e0 drivers/net/wireguard/device.c:257 netdev_run_todo+0xe1a/0x1000 net/core/dev.c:10693 default_device_exit_batch+0xa14/0xa90 net/core/dev.c:11769 ops_exit_list net/core/net_namespace.c:178 [inline] cleanup_net+0x89d/0xcc0 net/core/net_namespace.c:640 process_one_work kernel/workqueue.c:3231 [inline] process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK>
Fix this with skipping unecessary unparking while stopping a kthread.
Link: https://lkml.kernel.org/r/20240913214634.12557-1-frederic@kernel.org Fixes: 5c25b5ff89f0 ("workqueue: Tag bound workers with KTHREAD_IS_PER_CPU") Signed-off-by: Frederic Weisbecker frederic@kernel.org Reported-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com Tested-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com Suggested-by: Thomas Gleixner tglx@linutronix.de Cc: Hillf Danton hdanton@sina.com Cc: Tejun Heo tj@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/kthread.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -622,6 +622,8 @@ void kthread_unpark(struct task_struct * { struct kthread *kthread = to_kthread(k);
+ if (!test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)) + return; /* * Newly created kthread was parked when the CPU was offline. * The binding was lost and we need to set it again.