syzbot

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BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86887de8 of 8 bytes by task 2636 on cpu 1:
 data_alloc+0x280/0x2e0 kernel/printk/printk_ringbuffer.c:1102
 prb_reserve+0x807/0xaf0 kernel/printk/printk_ringbuffer.c:1685
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299
 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2448
 bt_err+0x9d/0xd0 net/bluetooth/lib.c:296
 __hci_cmd_sync_status_sk net/bluetooth/hci_sync.c:271 [inline]
 __hci_cmd_sync_status net/bluetooth/hci_sync.c:287 [inline]
 hci_read_local_features_sync net/bluetooth/hci_sync.c:3703 [inline]
 hci_init_stage_sync net/bluetooth/hci_sync.c:3618 [inline]
 hci_init1_sync net/bluetooth/hci_sync.c:3750 [inline]
 hci_init_sync net/bluetooth/hci_sync.c:4862 [inline]
 hci_dev_init_sync net/bluetooth/hci_sync.c:5054 [inline]
 hci_dev_open_sync+0xfa4/0x2290 net/bluetooth/hci_sync.c:5132
 hci_dev_do_open net/bluetooth/hci_core.c:430 [inline]
 hci_power_on+0xef/0x390 net/bluetooth/hci_core.c:959
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff86887de8 of 8 bytes by task 31335 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:479 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:775 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:921 [inline]
 prb_reserve+0x220/0xaf0 kernel/printk/printk_ringbuffer.c:1635
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299
 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2448
 bt_err+0x9d/0xd0 net/bluetooth/lib.c:296
 hci_cmd_timeout+0x97/0x140 net/bluetooth/hci_core.c:1469
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000039510 -> 0x00000000000eb7b8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 31335 Comm: kworker/u9:2 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: hci2 hci_cmd_timeout
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Bluetooth: hci2: command 0x1003 tx timeout