syzbot

__quota_error: 212 callbacks suppressed
==================================================================
BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86d2c6e0 of 88 bytes by task 29620 on cpu 1:
 prb_reserve+0x6e6/0xae0 kernel/printk/printk_ringbuffer.c:1690
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 mnt_warn_timestamp_expiry+0x1c3/0x200 fs/namespace.c:3305
 do_new_mount_fc fs/namespace.c:3779 [inline]
 do_new_mount+0x354/0x8d0 fs/namespace.c:3839
 path_mount+0x4d0/0xbc0 fs/namespace.c:4159
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4338
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4338
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86d2c6e0 of 8 bytes by task 30 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1c4/0x950 kernel/printk/printk_ringbuffer.c:2170
 desc_update_last_finalized+0x8f/0x170 kernel/printk/printk_ringbuffer.c:1570
 prb_final_commit+0x10d/0x150 kernel/printk/printk_ringbuffer.c:1839
 vprintk_store+0x88b/0x910 kernel/printk/printk.c:2381
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_deferred kernel/printk/printk.c:4714 [inline]
 _printk_deferred+0x82/0xb0 kernel/printk/printk.c:4723
 ___ratelimit+0x43a/0x460 lib/ratelimit.c:86
 __printk_ratelimit+0x1c/0x30 kernel/printk/printk.c:4739
 __quota_error+0x4f/0x110 fs/quota/dquot.c:139
 dquot_write_dquot fs/quota/dquot.c:675 [inline]
 quota_release_workfn+0x286/0x540 fs/quota/dquot.c:838
 process_one_work kernel/workqueue.c:3276 [inline]
 process_scheduled_works+0x513/0xa10 kernel/workqueue.c:3359
 worker_thread+0x58a/0x780 kernel/workqueue.c:3440
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000003af4 -> 0x0000000000005af4

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 30 Comm: kworker/u8:1 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: quota_events_unbound quota_release_workfn
==================================================================
Quota error (device loop9): dquot_write_dquot: Can't write quota structure (error -30). Quota may get out of sync!
EXT4-fs (loop9): Quota write (off=5120, len=1024) cancelled because transaction is not started
Quota error (device loop9): write_blk: dquota write failed
Quota error (device loop9): remove_free_dqentry: Can't write block (5) with free entries
EXT4-fs (loop9): Quota write (off=5120, len=1024) cancelled because transaction is not started
Quota error (device loop9): write_blk: dquota write failed
Quota error (device loop9): free_dqentry: Can't move quota data block (5) to free list
EXT4-fs (loop9): Quota write (off=8, len=24) cancelled because transaction is not started
Quota error (device loop9): v2_write_file_info: Can't write info structure
Quota error (device loop9): dquot_write_dquot: Can't write quota structure (error -30). Quota may get out of sync!
Quota error (device loop9): do_check_range: Getting dqdh_entries 15 out of range 0-14